# Clustering/Sharding impact on query performance **URL:** \ **Category:** Elasticsearch\ **Created:** [July 7, 2014, 1:51pm UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505 "2014-07-07T13:51:19Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![ElasticSearch\_Users\_](https://avatars.discourse-cdn.com/v4/letter/e/b4bc9f/32.png) [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)\ **Post date:** [July 7, 2014, 1:51pm UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/1 "2014-07-07T13:51:19Z")
Hi, _SCENARIO_ Our Elasticsearch database has ~2.5 million entries. Each entry has the three analyzed fields "match", "sec\_match" and "thi\_match" (all contains 3-20 words) that will be used in this query: > ES runs on two _types of servers_: (1) Real servers (system has direct access to real CPUs, no virtualization) of newest generation - Very performant! (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is generic for cloud services. See [https://gist.github.com/anonymous/3098b142c2bab51feecc](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and (2) CPU details. _ES settings:_ ES version 1.2.0 (jdk1.8.0\_05) ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) vm.max\_map\_count = 262144 ulimit -n 64000 ulimit -l unlimited index.number\_of\_shards: 1 index.number\_of\_replicas: 0 index.store.type: mmapfs threadpool.search.type: fixed threadpool.search.size: 75 threadpool.search.queue\_size: 5000 _Infrastructure_: As you can see above, we don't use the cluster feature of ES (1 shard, 0 replicas). The reason is that our hosting infrastructure is based on different providers. Upside: We aren't dependent on a single hosting provider. Downside: Our servers aren't in the same LAN. This means: - We cannot use ES sharding, because synchronisation via WAN (internet) seems not a useful solution. - So, every ES-server has the complete dataset and we configured only one shard and no replicas for higher performance. - We have a distribution process that updates the ES data on every host frequently. This process is fine for us, because updates aren't very often and perfect just-in-time ES synchronisation isn't necessary for our business case. - If a server goes down/crashs, the central loadbalancer removes it (the resulting minimal packet lost is acceptable). _PROBLEM_ For long query terms (6 and more keywords), we have very high CPU loads, even on the high performance server (1), and this leads to high response times: 1-4sec on server (1), 8-20sec on server (2). The system parameters while querying: - Very high load (usually 100%) for the thread responsible CPU (the other CPUs are idle in our test scenario) - No I/O load (the harddisks are fine) - No RAM bottlenecks So, we think the file caching is working fine, because we have no I/O problems and the garbage collector seams to be happy (jstat shows very few GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > _SUMMARY/ASSUMPTIONS_ - Our database size isn't very big and the query not very complex. - ES is designed for huge amount of data, but the key is clustering/sharding: Data distribution to many servers means smaller indices, smaller indices leads to fewer CPU load and short response times. - So, our database isn't big, but to big for a single CPU and this means especially low performance (virtual) CPUs can only be used in sharding environments. If we don't want to lost the provider independency, we have only the following two options: 1. Simpler query (I think not possible in our case) 2. Smaller database _QUESTIONS_ Are our assumptions correct? Especially: - Is clustering/sharding (also small indices) the main key to performance, that means the only possibility to prevent overloaded (virtual) CPUs? - Is it right that clustering is only useful/possible in LANs? - Do you have any ES configuration or architecture hints regarding our preference for using multiple hosting providers? Thank you. Rgds Fin -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/d1ad2e3c-6d16-493b-a066-1fa2a06a29a6%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/d1ad2e3c-6d16-493b-a066-1fa2a06a29a6%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![ElasticSearch\_Users\_](https://avatars.discourse-cdn.com/v4/letter/e/b4bc9f/32.png) [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)\ **Post date:** [July 10, 2014, 7:24am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/2 "2014-07-10T07:24:26Z")
Any hints? On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > Hi, > > _SCENARIO_ > > Our Elasticsearch database has ~2.5 million entries. Each entry has the > three analyzed fields "match", "sec\_match" and "thi\_match" (all contains > 3-20 words) that will be used in this query: > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > ES runs on two _types of servers_: > (1) Real servers (system has direct access to real CPUs, no > virtualization) of newest generation - Very performant! > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is generic > for cloud services. > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and > (2) CPU details. > > _ES settings:_ > ES version 1.2.0 (jdk1.8.0\_05) > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > vm.max\_map\_count = 262144 > ulimit -n 64000 > ulimit -l unlimited > index.number\_of\_shards: 1 > index.number\_of\_replicas: 0 > index.store.type: mmapfs > threadpool.search.type: fixed > threadpool.search.size: 75 > threadpool.search.queue\_size: 5000 > > _Infrastructure_: > As you can see above, we don't use the cluster feature of ES (1 shard, 0 > replicas). The reason is that our hosting infrastructure is based on > different providers. > Upside: We aren't dependent on a single hosting provider. Downside: Our > servers aren't in the same LAN. > > This means: > > - We cannot use ES sharding, because synchronisation via WAN (internet) > seems not a useful solution. > - So, every ES-server has the complete dataset and we configured only one > shard and no replicas for higher performance. > - We have a distribution process that updates the ES data on every host > frequently. This process is fine for us, because updates aren't very often > and perfect just-in-time ES synchronisation isn't necessary for our > business case. > - If a server goes down/crashs, the central loadbalancer removes it (the > resulting minimal packet lost is acceptable). > > _PROBLEM_ > > For long query terms (6 and more keywords), we have very high CPU loads, > even on the high performance server (1), and this leads to high response > times: 1-4sec on server (1), 8-20sec on server (2). The system parameters > while querying: > > - Very high load (usually 100%) for the thread responsible CPU (the other > CPUs are idle in our test scenario) > - No I/O load (the harddisks are fine) > - No RAM bottlenecks > > So, we think the file caching is working fine, because we have no I/O > problems and the garbage collector seams to be happy (jstat shows very few > GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > _SUMMARY/ASSUMPTIONS_ > > - Our database size isn't very big and the query not very complex. > - ES is designed for huge amount of data, but the key is > clustering/sharding: Data distribution to many servers means smaller > indices, smaller indices leads to fewer CPU load and short response times. > - So, our database isn't big, but to big for a single CPU and this means > especially low performance (virtual) CPUs can only be used in sharding > environments. > > If we don't want to lost the provider independency, we have only the > following two options: > > 1. Simpler query (I think not possible in our case) > 2. Smaller database > > _QUESTIONS_ > > Are our assumptions correct? Especially: > > - Is clustering/sharding (also small indices) the main key to performance, > that means the only possibility to prevent overloaded (virtual) CPUs? > - Is it right that clustering is only useful/possible in LANs? > - Do you have any ES configuration or architecture hints regarding our > preference for using multiple hosting providers? > > Thank you. Rgds > Fin -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/18434f95-5587-48fe-bc6e-214155decec0%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/18434f95-5587-48fe-bc6e-214155decec0%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![Kireet\_Reddy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kireet_reddy/32/1071_2.png) [@Kireet\_Reddy](https://discuss.elastic.co/u/Kireet_Reddy)\ **Post date:** [July 11, 2014, 1:02am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/3 "2014-07-11T01:02:50Z")
I would test using multiple primary shards on a single machine. Since your dataset seems to fit into RAM, this could help for these longer latency queries. On Thursday, July 10, 2014 12:24:26 AM UTC-7, Fin Sekun wrote: > Any hints? > > On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > > > Hi, > > > > _SCENARIO_ > > > > Our Elasticsearch database has ~2.5 million entries. Each entry has the > > three analyzed fields "match", "sec\_match" and "thi\_match" (all contains > > 3-20 words) that will be used in this query: > > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > > > ES runs on two _types of servers_: > > (1) Real servers (system has direct access to real CPUs, no > > virtualization) of newest generation - Very performant! > > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is generic > > for cloud services. > > > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and > > (2) CPU details. > > > > _ES settings:_ > > ES version 1.2.0 (jdk1.8.0\_05) > > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > > vm.max\_map\_count = 262144 > > ulimit -n 64000 > > ulimit -l unlimited > > index.number\_of\_shards: 1 > > index.number\_of\_replicas: 0 > > index.store.type: mmapfs > > threadpool.search.type: fixed > > threadpool.search.size: 75 > > threadpool.search.queue\_size: 5000 > > > > _Infrastructure_: > > As you can see above, we don't use the cluster feature of ES (1 shard, 0 > > replicas). The reason is that our hosting infrastructure is based on > > different providers. > > Upside: We aren't dependent on a single hosting provider. Downside: Our > > servers aren't in the same LAN. > > > > This means: > > > > - We cannot use ES sharding, because synchronisation via WAN (internet) > > seems not a useful solution. > > - So, every ES-server has the complete dataset and we configured only one > > shard and no replicas for higher performance. > > - We have a distribution process that updates the ES data on every host > > frequently. This process is fine for us, because updates aren't very often > > and perfect just-in-time ES synchronisation isn't necessary for our > > business case. > > - If a server goes down/crashs, the central loadbalancer removes it (the > > resulting minimal packet lost is acceptable). > > > > _PROBLEM_ > > > > For long query terms (6 and more keywords), we have very high CPU loads, > > even on the high performance server (1), and this leads to high response > > times: 1-4sec on server (1), 8-20sec on server (2). The system parameters > > while querying: > > > > - Very high load (usually 100%) for the thread responsible CPU (the other > > CPUs are idle in our test scenario) > > - No I/O load (the harddisks are fine) > > - No RAM bottlenecks > > > > So, we think the file caching is working fine, because we have no I/O > > problems and the garbage collector seams to be happy (jstat shows very few > > GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > > > _SUMMARY/ASSUMPTIONS_ > > > > - Our database size isn't very big and the query not very complex. > > - ES is designed for huge amount of data, but the key is > > clustering/sharding: Data distribution to many servers means smaller > > indices, smaller indices leads to fewer CPU load and short response times. > > - So, our database isn't big, but to big for a single CPU and this means > > especially low performance (virtual) CPUs can only be used in sharding > > environments. > > > > If we don't want to lost the provider independency, we have only the > > following two options: > > > > 1. Simpler query (I think not possible in our case) > > 2. Smaller database > > > > _QUESTIONS_ > > > > Are our assumptions correct? Especially: > > > > - Is clustering/sharding (also small indices) the main key to > > performance, that means the only possibility to prevent overloaded > > (virtual) CPUs? > > - Is it right that clustering is only useful/possible in LANs? > > - Do you have any ES configuration or architecture hints regarding our > > preference for using multiple hosting providers? > > > > Thank you. Rgds > > Fin -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/046b78ca-9173-4fa0-ae5d-309a716c9dc3%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/046b78ca-9173-4fa0-ae5d-309a716c9dc3%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![ElasticSearch\_Users\_](https://avatars.discourse-cdn.com/v4/letter/e/b4bc9f/32.png) [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)\ **Post date:** [July 20, 2014, 8:01am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/4 "2014-07-20T08:01:21Z")
Hi Kireet, thanks for your answer and sorry for the late response. More shards doesn't help. It will slow down the system because each shard takes quite some overhead to maintain a Lucene index and, the smaller the shards, the bigger the overhead. Having more shards enhances the indexing performance and allows to distribute a big index across machines, but I don't have a cluster with a lot of machines. I could observe this negative effects while testing with 20 shards. It would be very cool if somebody could answer/comment to the question summarized at the end of my post. Thanks again. On Friday, July 11, 2014 3:02:50 AM UTC+2, Kireet Reddy wrote: > I would test using multiple primary shards on a single machine. Since your > dataset seems to fit into RAM, this could help for these longer latency > queries. > > On Thursday, July 10, 2014 12:24:26 AM UTC-7, Fin Sekun wrote: > > > Any hints? > > > > On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > > > > > Hi, > > > > > > _SCENARIO_ > > > > > > Our Elasticsearch database has ~2.5 million entries. Each entry has the > > > three analyzed fields "match", "sec\_match" and "thi\_match" (all contains > > > 3-20 words) that will be used in this query: > > > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > > > > > ES runs on two _types of servers_: > > > (1) Real servers (system has direct access to real CPUs, no > > > virtualization) of newest generation - Very performant! > > > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is generic > > > for cloud services. > > > > > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and > > > (2) CPU details. > > > > > > _ES settings:_ > > > ES version 1.2.0 (jdk1.8.0\_05) > > > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > > > vm.max\_map\_count = 262144 > > > ulimit -n 64000 > > > ulimit -l unlimited > > > index.number\_of\_shards: 1 > > > index.number\_of\_replicas: 0 > > > index.store.type: mmapfs > > > threadpool.search.type: fixed > > > threadpool.search.size: 75 > > > threadpool.search.queue\_size: 5000 > > > > > > _Infrastructure_: > > > As you can see above, we don't use the cluster feature of ES (1 shard, 0 > > > replicas). The reason is that our hosting infrastructure is based on > > > different providers. > > > Upside: We aren't dependent on a single hosting provider. Downside: Our > > > servers aren't in the same LAN. > > > > > > This means: > > > > > > - We cannot use ES sharding, because synchronisation via WAN (internet) > > > seems not a useful solution. > > > - So, every ES-server has the complete dataset and we configured only > > > one shard and no replicas for higher performance. > > > - We have a distribution process that updates the ES data on every host > > > frequently. This process is fine for us, because updates aren't very often > > > and perfect just-in-time ES synchronisation isn't necessary for our > > > business case. > > > - If a server goes down/crashs, the central loadbalancer removes it (the > > > resulting minimal packet lost is acceptable). > > > > > > _PROBLEM_ > > > > > > For long query terms (6 and more keywords), we have very high CPU loads, > > > even on the high performance server (1), and this leads to high response > > > times: 1-4sec on server (1), 8-20sec on server (2). The system parameters > > > while querying: > > > > > > - Very high load (usually 100%) for the thread responsible CPU (the > > > other CPUs are idle in our test scenario) > > > - No I/O load (the harddisks are fine) > > > - No RAM bottlenecks > > > > > > So, we think the file caching is working fine, because we have no I/O > > > problems and the garbage collector seams to be happy (jstat shows very few > > > GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > > > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > > > > > _SUMMARY/ASSUMPTIONS_ > > > > > > - Our database size isn't very big and the query not very complex. > > > - ES is designed for huge amount of data, but the key is > > > clustering/sharding: Data distribution to many servers means smaller > > > indices, smaller indices leads to fewer CPU load and short response times. > > > - So, our database isn't big, but to big for a single CPU and this means > > > especially low performance (virtual) CPUs can only be used in sharding > > > environments. > > > > > > If we don't want to lost the provider independency, we have only the > > > following two options: > > > > > > 1. Simpler query (I think not possible in our case) > > > 2. Smaller database > > > > > > _QUESTIONS_ > > > > > > Are our assumptions correct? Especially: > > > > > > - Is clustering/sharding (also small indices) the main key to > > > performance, that means the only possibility to prevent overloaded > > > (virtual) CPUs? > > > - Is it right that clustering is only useful/possible in LANs? > > > - Do you have any ES configuration or architecture hints regarding our > > > preference for using multiple hosting providers? > > > > > > Thank you. Rgds > > > Fin -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![jprante](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jprante/32/44941_2.png) [@jprante](https://discuss.elastic.co/u/jprante)\ **Post date:** [July 20, 2014, 10:19am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/5 "2014-07-20T10:19:30Z")
Your setup looks quite uncommon but I do not comment on that any further as you seem to know what you do, just the idea of creating single shard clusters and distributing them across data centers is counterintuitive to the advantages of an ES installation. I recommend revising your settings, they look very odd. Why did you change the defaults? The heap size of 512m, this is definitely preventing more shards. Short answers to your questions - no, clustering / sharding is not the main key to performance, it is crucial for scalability - you can cluster not only in LANs, but over all kinds of hosts as long as they can respond fast "enough". Important for ES nodes is low latency on the network. High latency between nodes induces instabilities into ES which makes life hard as an operator. - if you mean client perspective, you should look at the Tribe node that can span multiple clusters [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/modules-tribe.html) Jörg On Mon, Jul 7, 2014 at 3:51 PM, 'Fin Sekun' via elasticsearch \< [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com)\> wrote: > _QUESTIONS_ > > Are our assumptions correct? Especially: > > - Is clustering/sharding (also small indices) the main key to performance, > that means the only possibility to prevent overloaded (virtual) CPUs? > - Is it right that clustering is only useful/possible in LANs? > - Do you have any ES configuration or architecture hints regarding our > preference for using multiple hosting providers? -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFdT\_08OkwAYy10zOizv9%2BJCpcLRbDYHq%2B2S5Tbq1ViYA%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFdT_08OkwAYy10zOizv9%2BJCpcLRbDYHq%2B2S5Tbq1ViYA%40mail.gmail.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![smonasco\_2](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@smonasco\_2](https://discuss.elastic.co/u/smonasco_2)\ **Post date:** [July 21, 2014, 4:44am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/6 "2014-07-21T04:44:18Z")
Your query looks weird it says filtered but has no filter. It specifies boost but has no sort. I would remove the filtered, either remove boost or force the sort on score and ensure I was using index options of offsets (this also includes term frequencies and doc counts and pretty much everything precompiled to do the TF idf thing) -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/9d9fd340-a001-42e5-afa1-b1a78bdca111%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/9d9fd340-a001-42e5-afa1-b1a78bdca111%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![Kireet\_Reddy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kireet_reddy/32/1071_2.png) [@Kireet\_Reddy](https://discuss.elastic.co/u/Kireet_Reddy)\ **Post date:** [July 21, 2014, 3:46pm UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/7 "2014-07-21T15:46:19Z")
My working assumption had been that elasticsearch executes queries across all shards in parallel and then merges the results. So maybe shards \<= cpu cores would help in this case where there is only one concurrent query. But I have never tested this assumption, out of curiosity during the 20 shard test did you still only see 1 cpu being used? Did you try 2 shards and get the same results? On Jul 20, 2014, at 1:01 AM, 'Fin Sekun' via elasticsearch [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com) wrote: > Hi Kireet, thanks for your answer and sorry for the late response. More shards doesn't help. It will slow down the system because each shard takes quite some overhead to maintain a Lucene index and, the smaller the shards, the bigger the overhead. Having more shards enhances the indexing performance and allows to distribute a big index across machines, but I don't have a cluster with a lot of machines. I could observe this negative effects while testing with 20 shards. > > It would be very cool if somebody could answer/comment to the question summarized at the end of my post. Thanks again. > > On Friday, July 11, 2014 3:02:50 AM UTC+2, Kireet Reddy wrote: > I would test using multiple primary shards on a single machine. Since your dataset seems to fit into RAM, this could help for these longer latency queries. > > On Thursday, July 10, 2014 12:24:26 AM UTC-7, Fin Sekun wrote: > Any hints? > > On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > > Hi, > > SCENARIO > > Our Elasticsearch database has ~2.5 million entries. Each entry has the three analyzed fields "match", "sec\_match" and "thi\_match" (all contains 3-20 words) that will be used in this query: > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > ES runs on two types of servers: > (1) Real servers (system has direct access to real CPUs, no virtualization) of newest generation - Very performant! > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is generic for cloud services. > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and (2) CPU details. > > ES settings: > ES version 1.2.0 (jdk1.8.0\_05) > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > vm.max\_map\_count = 262144 > ulimit -n 64000 > ulimit -l unlimited > index.number\_of\_shards: 1 > index.number\_of\_replicas: 0 > index.store.type: mmapfs > threadpool.search.type: fixed > threadpool.search.size: 75 > threadpool.search.queue\_size: 5000 > > Infrastructure: > As you can see above, we don't use the cluster feature of ES (1 shard, 0 replicas). The reason is that our hosting infrastructure is based on different providers. > Upside: We aren't dependent on a single hosting provider. Downside: Our servers aren't in the same LAN. > > This means: > > - We cannot use ES sharding, because synchronisation via WAN (internet) seems not a useful solution. > - So, every ES-server has the complete dataset and we configured only one shard and no replicas for higher performance. > - We have a distribution process that updates the ES data on every host frequently. This process is fine for us, because updates aren't very often and perfect just-in-time ES synchronisation isn't necessary for our business case. > - If a server goes down/crashs, the central loadbalancer removes it (the resulting minimal packet lost is acceptable). > > PROBLEM > > For long query terms (6 and more keywords), we have very high CPU loads, even on the high performance server (1), and this leads to high response times: 1-4sec on server (1), 8-20sec on server (2). The system parameters while querying: > > - Very high load (usually 100%) for the thread responsible CPU (the other CPUs are idle in our test scenario) > - No I/O load (the harddisks are fine) > - No RAM bottlenecks > > So, we think the file caching is working fine, because we have no I/O problems and the garbage collector seams to be happy (jstat shows very few GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > SUMMARY/ASSUMPTIONS > > - Our database size isn't very big and the query not very complex. > - ES is designed for huge amount of data, but the key is clustering/sharding: Data distribution to many servers means smaller indices, smaller indices leads to fewer CPU load and short response times. > - So, our database isn't big, but to big for a single CPU and this means especially low performance (virtual) CPUs can only be used in sharding environments. > > If we don't want to lost the provider independency, we have only the following two options: > > 1. Simpler query (I think not possible in our case) > 2. Smaller database > > QUESTIONS > > Are our assumptions correct? Especially: > > - Is clustering/sharding (also small indices) the main key to performance, that means the only possibility to prevent overloaded (virtual) CPUs? > - Is it right that clustering is only useful/possible in LANs? > - Do you have any ES configuration or architecture hints regarding our preference for using multiple hosting providers? > > Thank you. Rgds > Fin > > -- > You received this message because you are subscribed to a topic in the Google Groups "elasticsearch" group. > To unsubscribe from this topic, visit [https://groups.google.com/d/topic/elasticsearch/TpEboTt\_8FY/unsubscribe](https://groups.google.com/d/topic/elasticsearch/TpEboTt_8FY/unsubscribe). > To unsubscribe from this group and all its topics, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com). > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. 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**Author:** ![ElasticSearch\_Users\_](https://avatars.discourse-cdn.com/v4/letter/e/b4bc9f/32.png) [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)\ **Post date:** [July 27, 2014, 11:40am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/8 "2014-07-27T11:40:27Z")
Thanks for your answers. @Jörg: Of course sharding is primarly curcial for scalability, but it seems (and nobody disagreed in this posts) that big indices lead to high CPU load, so sharding is curcial for performance too. @smonasco: - The query will be put together by an application that sets always a filter field. I would be suprised if ES doesn't efficiently ignore this part. - There is no sort field, so ES sorts by score. - Offsets etc. are default for alle analyzed fields. @Kireet: Hm, I think only one CPU was being used, but I'm not sure anymore, the test was a long time ago. As soon as I have time I will test with number of shards smaller than number of CPUs. On Monday, July 21, 2014 5:46:38 PM UTC+2, Kireet Reddy wrote: > My working assumption had been that elasticsearch executes queries across > all shards in parallel and then merges the results. So maybe shards \<= cpu > cores would help in this case where there is only one concurrent query. But > I have never tested this assumption, out of curiosity during the 20 shard > test did you still only see 1 cpu being used? Did you try 2 shards and get > the same results? > > On Jul 20, 2014, at 1:01 AM, 'Fin Sekun' via elasticsearch \< > [elasti...@googlegroups.com](mailto:elasti...@googlegroups.com) \\> wrote: > > Hi Kireet, thanks for your answer and sorry for the late response. More > shards doesn't help. It will slow down the system because each shard takes > quite some overhead to maintain a Lucene index and, the smaller the shards, > the bigger the overhead. Having more shards enhances the indexing > performance and allows to distribute a big index across machines, but I > don't have a cluster with a lot of machines. I could observe this negative > effects while testing with 20 shards. > > It would be very cool if somebody could answer/comment to the question > summarized at the end of my post. Thanks again. > > On Friday, July 11, 2014 3:02:50 AM UTC+2, Kireet Reddy wrote: > > > I would test using multiple primary shards on a single machine. Since > > your dataset seems to fit into RAM, this could help for these longer > > latency queries. > > > > On Thursday, July 10, 2014 12:24:26 AM UTC-7, Fin Sekun wrote: > > > > > Any hints? > > > > > > On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > > > > > > > Hi, > > > > > > > > _SCENARIO_ > > > > > > > > Our Elasticsearch database has ~2.5 million entries. Each entry has the > > > > three analyzed fields "match", "sec\_match" and "thi\_match" (all contains > > > > 3-20 words) that will be used in this query: > > > > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > > > > > > > ES runs on two _types of servers_: > > > > (1) Real servers (system has direct access to real CPUs, no > > > > virtualization) of newest generation - Very performant! > > > > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is > > > > generic for cloud services. > > > > > > > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) and > > > > (2) CPU details. > > > > > > > > _ES settings:_ > > > > ES version 1.2.0 (jdk1.8.0\_05) > > > > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > > > > vm.max\_map\_count = 262144 > > > > ulimit -n 64000 > > > > ulimit -l unlimited > > > > index.number\_of\_shards: 1 > > > > index.number\_of\_replicas: 0 > > > > index.store.type: mmapfs > > > > threadpool.search.type: fixed > > > > threadpool.search.size: 75 > > > > threadpool.search.queue\_size: 5000 > > > > > > > > _Infrastructure_: > > > > As you can see above, we don't use the cluster feature of ES (1 shard, > > > > 0 replicas). The reason is that our hosting infrastructure is based on > > > > different providers. > > > > Upside: We aren't dependent on a single hosting provider. Downside: Our > > > > servers aren't in the same LAN. > > > > > > > > This means: > > > > > > > > - We cannot use ES sharding, because synchronisation via WAN (internet) > > > > seems not a useful solution. > > > > - So, every ES-server has the complete dataset and we configured only > > > > one shard and no replicas for higher performance. > > > > - We have a distribution process that updates the ES data on every host > > > > frequently. This process is fine for us, because updates aren't very often > > > > and perfect just-in-time ES synchronisation isn't necessary for our > > > > business case. > > > > - If a server goes down/crashs, the central loadbalancer removes it > > > > (the resulting minimal packet lost is acceptable). > > > > > > > > _PROBLEM_ > > > > > > > > For long query terms (6 and more keywords), we have very high CPU > > > > loads, even on the high performance server (1), and this leads to high > > > > response times: 1-4sec on server (1), 8-20sec on server (2). The system > > > > parameters while querying: > > > > > > > > - Very high load (usually 100%) for the thread responsible CPU (the > > > > other CPUs are idle in our test scenario) > > > > - No I/O load (the harddisks are fine) > > > > - No RAM bottlenecks > > > > > > > > So, we think the file caching is working fine, because we have no I/O > > > > problems and the garbage collector seams to be happy (jstat shows very few > > > > GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > > > > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > > > > > > > _SUMMARY/ASSUMPTIONS_ > > > > > > > > - Our database size isn't very big and the query not very complex. > > > > - ES is designed for huge amount of data, but the key is > > > > clustering/sharding: Data distribution to many servers means smaller > > > > indices, smaller indices leads to fewer CPU load and short response times. > > > > - So, our database isn't big, but to big for a single CPU and this > > > > means especially low performance (virtual) CPUs can only be used in > > > > sharding environments. > > > > > > > > If we don't want to lost the provider independency, we have only the > > > > following two options: > > > > > > > > 1. Simpler query (I think not possible in our case) > > > > 2. Smaller database > > > > > > > > _QUESTIONS_ > > > > > > > > Are our assumptions correct? Especially: > > > > > > > > - Is clustering/sharding (also small indices) the main key to > > > > performance, that means the only possibility to prevent overloaded > > > > (virtual) CPUs? > > > > - Is it right that clustering is only useful/possible in LANs? > > > > - Do you have any ES configuration or architecture hints regarding our > > > > preference for using multiple hosting providers? > > > > > > > > Thank you. Rgds > > > > Fin > > -- > You received this message because you are subscribed to a topic in the > Google Groups "elasticsearch" group. > To unsubscribe from this topic, visit > [https://groups.google.com/d/topic/elasticsearch/TpEboTt\_8FY/unsubscribe](https://groups.google.com/d/topic/elasticsearch/TpEboTt_8FY/unsubscribe). > To unsubscribe from this group and all its topics, send an email to > [elasticsearc...@googlegroups.com](mailto:elasticsearc...@googlegroups.com) \. > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com) > [https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com?utm_medium=email&utm_source=footer) > . > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![smonasco\_2](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@smonasco\_2](https://discuss.elastic.co/u/smonasco_2)\ **Post date:** [July 27, 2014, 1:30pm UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/9 "2014-07-27T13:30:50Z")
I don't think big shards lead to high court load during query time. Burst tries, the tree structure behind Lucene's inverse indexes, are setup so that you only have to do up to 2 string compares (and it would seem usually just one) to transverse them. So your CPU load should be dependent on the number of (term, field)'s you're matching \* number of segments (of course there may be some paged in factor of being able to fully utilize a cycle which might be dependent on the depth of the tree (which in turn keeps common terms closer to the top to prevent too many reads and the depth for uncommon terms is maxed at term length) and what other threads are currently running. Given the way tree transverses (and burst tries un particular) work I would only imagine fewer trees would mean fewer cycles. With one more read and no more full string comparisons you can get exponentially farther. On Jul 27, 2014 5:40 AM, "'Fin Sekun' via elasticsearch" \< [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com)\> wrote: > Thanks for your answers. > > @Jörg: > Of course sharding is primarly curcial for scalability, but it seems (and > nobody disagreed in this posts) that big indices lead to high CPU load, so > sharding is curcial for performance too. > > @smonasco: > > - The query will be put together by an application that sets always a > filter field. I would be suprised if ES doesn't efficiently ignore this > part. > - There is no sort field, so ES sorts by score. > - Offsets etc. are default for alle analyzed fields. > > @Kireet: > Hm, I think only one CPU was being used, but I'm not sure anymore, the > test was a long time ago. As soon as I have time I will test with number of > shards smaller than number of CPUs. > > On Monday, July 21, 2014 5:46:38 PM UTC+2, Kireet Reddy wrote: > > > My working assumption had been that elasticsearch executes queries across > > all shards in parallel and then merges the results. So maybe shards \<= cpu > > cores would help in this case where there is only one concurrent query. But > > I have never tested this assumption, out of curiosity during the 20 shard > > test did you still only see 1 cpu being used? Did you try 2 shards and get > > the same results? > > > > On Jul 20, 2014, at 1:01 AM, 'Fin Sekun' via elasticsearch \< > > [elasti...@googlegroups.com](mailto:elasti...@googlegroups.com)\> wrote: > > > > Hi Kireet, thanks for your answer and sorry for the late response. More > > shards doesn't help. It will slow down the system because each shard takes > > quite some overhead to maintain a Lucene index and, the smaller the shards, > > the bigger the overhead. Having more shards enhances the indexing > > performance and allows to distribute a big index across machines, but I > > don't have a cluster with a lot of machines. I could observe this negative > > effects while testing with 20 shards. > > > > It would be very cool if somebody could answer/comment to the question > > summarized at the end of my post. Thanks again. > > > > On Friday, July 11, 2014 3:02:50 AM UTC+2, Kireet Reddy wrote: > > > > > I would test using multiple primary shards on a single machine. Since > > > your dataset seems to fit into RAM, this could help for these longer > > > latency queries. > > > > > > On Thursday, July 10, 2014 12:24:26 AM UTC-7, Fin Sekun wrote: > > > > > > > Any hints? > > > > > > > > On Monday, July 7, 2014 3:51:19 PM UTC+2, Fin Sekun wrote: > > > > > > > > > Hi, > > > > > > > > > > _SCENARIO_ > > > > > > > > > > Our Elasticsearch database has ~2.5 million entries. Each entry has > > > > > the three analyzed fields "match", "sec\_match" and "thi\_match" (all > > > > > contains 3-20 words) that will be used in this query: > > > > > [gist:a8d1142512e5625e4e91 · GitHub](https://gist.github.com/anonymous/a8d1142512e5625e4e91) > > > > > > > > > > ES runs on two _types of servers_: > > > > > (1) Real servers (system has direct access to real CPUs, no > > > > > virtualization) of newest generation - Very performant! > > > > > (2) Cloud servers with virtualized CPUs - Poor CPUs, but this is > > > > > generic for cloud services. > > > > > > > > > > See [gist:3098b142c2bab51feecc · GitHub](https://gist.github.com/anonymous/3098b142c2bab51feecc) for (1) > > > > > and (2) CPU details. > > > > > > > > > > _ES settings:_ > > > > > ES version 1.2.0 (jdk1.8.0\_05) > > > > > ES\_HEAP\_SIZE = 512m (we also tested with 1024m with same results) > > > > > vm.max\_map\_count = 262144 > > > > > ulimit -n 64000 > > > > > ulimit -l unlimited > > > > > index.number\_of\_shards: 1 > > > > > index.number\_of\_replicas: 0 > > > > > index.store.type: mmapfs > > > > > threadpool.search.type: fixed > > > > > threadpool.search.size: 75 > > > > > threadpool.search.queue\_size: 5000 > > > > > > > > > > _Infrastructure_: > > > > > As you can see above, we don't use the cluster feature of ES (1 shard, > > > > > 0 replicas). The reason is that our hosting infrastructure is based on > > > > > different providers. > > > > > Upside: We aren't dependent on a single hosting provider. Downside: > > > > > Our servers aren't in the same LAN. > > > > > > > > > > This means: > > > > > > > > > > - We cannot use ES sharding, because synchronisation via WAN > > > > > (internet) seems not a useful solution. > > > > > - So, every ES-server has the complete dataset and we configured only > > > > > one shard and no replicas for higher performance. > > > > > - We have a distribution process that updates the ES data on every > > > > > host frequently. This process is fine for us, because updates aren't very > > > > > often and perfect just-in-time ES synchronisation isn't necessary for our > > > > > business case. > > > > > - If a server goes down/crashs, the central loadbalancer removes it > > > > > (the resulting minimal packet lost is acceptable). > > > > > > > > > > _PROBLEM_ > > > > > > > > > > For long query terms (6 and more keywords), we have very high CPU > > > > > loads, even on the high performance server (1), and this leads to high > > > > > response times: 1-4sec on server (1), 8-20sec on server (2). The system > > > > > parameters while querying: > > > > > > > > > > - Very high load (usually 100%) for the thread responsible CPU (the > > > > > other CPUs are idle in our test scenario) > > > > > - No I/O load (the harddisks are fine) > > > > > - No RAM bottlenecks > > > > > > > > > > So, we think the file caching is working fine, because we have no I/O > > > > > problems and the garbage collector seams to be happy (jstat shows very few > > > > > GCs). The CPU is the problem, and ES hot-threads point to the Scorer module: > > > > > [Elasticsearch Hot-Threads · GitHub](https://gist.github.com/anonymous/9cecfd512cb533114b7d) > > > > > > > > > > _SUMMARY/ASSUMPTIONS_ > > > > > > > > > > - Our database size isn't very big and the query not very complex. > > > > > - ES is designed for huge amount of data, but the key is > > > > > clustering/sharding: Data distribution to many servers means smaller > > > > > indices, smaller indices leads to fewer CPU load and short response times. > > > > > - So, our database isn't big, but to big for a single CPU and this > > > > > means especially low performance (virtual) CPUs can only be used in > > > > > sharding environments. > > > > > > > > > > If we don't want to lost the provider independency, we have only the > > > > > following two options: > > > > > > > > > > 1. Simpler query (I think not possible in our case) > > > > > 2. Smaller database > > > > > > > > > > _QUESTIONS_ > > > > > > > > > > Are our assumptions correct? Especially: > > > > > > > > > > - Is clustering/sharding (also small indices) the main key to > > > > > performance, that means the only possibility to prevent overloaded > > > > > (virtual) CPUs? > > > > > - Is it right that clustering is only useful/possible in LANs? > > > > > - Do you have any ES configuration or architecture hints regarding our > > > > > preference for using multiple hosting providers? > > > > > > > > > > Thank you. Rgds > > > > > Fin > > > > -- > > You received this message because you are subscribed to a topic in the > > Google Groups "elasticsearch" group. > > To unsubscribe from this topic, visit [https://groups.google.com/d/](https://groups.google.com/d/) > > topic/elasticsearch/TpEboTt\_8FY/unsubscribe. > > To unsubscribe from this group and all its topics, send an email to > > [elasticsearc...@googlegroups.com](mailto:elasticsearc...@googlegroups.com). > > To view this discussion on the web visit [https://groups.google.com/d/](https://groups.google.com/d/) > > msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904% > > [40googlegroups.com](http://40googlegroups.com) > > [https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/7e1b3a52-23b4-4a22-8433-985e07ae7904%40googlegroups.com?utm_medium=email&utm_source=footer) > > . > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > -- > > You received this message because you are subscribed to a topic in the > > Google Groups "elasticsearch" group. > > To unsubscribe from this topic, visit > > [https://groups.google.com/d/topic/elasticsearch/TpEboTt\_8FY/unsubscribe](https://groups.google.com/d/topic/elasticsearch/TpEboTt_8FY/unsubscribe). > > To unsubscribe from this group and all its topics, send an email to > > [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > > To view this discussion on the web visit > > [https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com) > > [https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/fac66eb6-8b1f-4aaa-848b-fe54654dfdc5%40googlegroups.com?utm_medium=email&utm_source=footer) > > . > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. 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**Author:** ![jprante](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jprante/32/44941_2.png) [@jprante](https://discuss.elastic.co/u/jprante)\ **Post date:** [July 28, 2014, 2:20pm UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/10 "2014-07-28T14:20:58Z")
I think you confuse things and I disagree. If you see high CPU load, it is because your system runs tight of resources and tries harder to tackle these challenge automatically, e.g. by higher GC. It is not ES generating higher load just because of the index document count. There is no relation between a system tight on resources and the index document count of ES. If you add nodes, the shards distribute over more nodes, this means scalability. When you scale out your system, you can process a higher number of queries concurrently. So with constant index document count, you have all kinds of CPU load, low and high. Jörg On Sun, Jul 27, 2014 at 1:40 PM, 'Fin Sekun' via elasticsearch \< [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com)\> wrote: > Thanks for your answers. > > @Jörg: > Of course sharding is primarly curcial for scalability, but it seems (and > nobody disagreed in this posts) that big indices lead to high CPU load, so > sharding is curcial for performance too. -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAKdsXoHecJ5cXAYN30rTKR4xqo6GzzonQXAnL703HNBWH7XFVQ%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAKdsXoHecJ5cXAYN30rTKR4xqo6GzzonQXAnL703HNBWH7XFVQ%40mail.gmail.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 1:12am UTC](https://discuss.elastic.co/t/clustering-sharding-impact-on-query-performance/18505/11 "2017-07-06T01:12:47Z")