# Optimizing a single node ES instance for throughput
**URL:** https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808
**Category:** Elasticsearch
**Created:** [June 21, 2022, 10:22pm UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808 "2022-06-21T22:22:05Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@dmh43](https://discuss.elastic.co/u/dmh43)
#### Post date: [June 21, 2022, 10:22pm UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/1 "2022-06-21T22:22:05Z")
I have a single large (500GB ram and 128 cores) machine that I have indexed a corpus of around 1TB in size. The documents vary in length, from very short (~100 characters) to very long (a single documents that is \> 100 MB in size).
Requests to the index arrive as part of a batch process, so I do not have strict requirements on latency, I mostly want to maximize retrieval throughput (I rarely index new documents).
My index has 50 shards, and requests are made to the index using multiple connections. I'm finding that if I have too many connections open, then I get `ScanError: Scroll request has only succeeded on 25 (+0 skiped) shards out of 50` even though the machine does not seem particularly loaded. If I do not open enough connections, then the machine is mostly idle and throughput is low. I'm finding that the optimal number of connections depends on the queries I am making.
My questions:
- Why am I getting the `ScanError` reported above? Is there some way to get some details as to what caused certain shards to not succeed? Do I just need to increase the number of shards?
- Do you have any other suggestions when it comes to optimizing throughput for a single node cluster? Or even for ES clusters in general.
- Is there some better way to choose the number of connections?
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### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [June 21, 2022, 10:30pm UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/2 "2022-06-21T22:30:22Z")
Welcome to our community! 😃
You'd be better off splitting this host up into a few nodes. You're already running risk of losing data due to being on a single host, but a few nodes (eg 3) would probably make better use of the overall resources.
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### Author:  [@dmh43](https://discuss.elastic.co/u/dmh43)
#### Post date: [June 22, 2022, 2:22pm UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/3 "2022-06-22T14:22:01Z")
Thanks! Why would spinning up additional nodes make better use of the computational resources? I would expect that there is some configurations I can change to allow a single node to take advantage of all it's resources.
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### Author:  [@rugenl](https://discuss.elastic.co/u/rugenl)
#### Post date: [June 22, 2022, 5:47pm UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/4 "2022-06-22T17:47:13Z")
Look for articles like this: [Running Multiple Elasticsearch 6.x Instances on a Single Server](https://eitr.tech/blog/2019/01/17/multiple-es-nodes-single-server.html)
Java heap is limited to about 32G for best performance because it's Java, so multiple instances let you have more heap.
Anyone running in a cloud resource is highly likely to be sharing a host.
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### Author:  [@sandeepkanabar](https://discuss.elastic.co/u/sandeepkanabar)
#### Post date: [June 30, 2022, 6:20am UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/5 "2022-06-30T06:20:46Z")
> [@dmh43](#):
>
> I have a single large (500GB ram
Because the max recommended ES heap size is 32 GB. See this - [Use more than 32GB for heap - #2 by spinscale](https://discuss.elastic.co/t/use-more-than-32gb-for-heap/204422/2). So in effect, you aren't able to fully utilise the full RAM.
So you can either set up multiple instances or you can set-up multiple VM (nodes). cost-wise it would actually work out lesser for you.
Also have a look at [Managing and troubleshooting Elasticsearch memory | Elastic Blog](https://www.elastic.co/blog/managing-and-troubleshooting-elasticsearch-memory)
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### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [June 30, 2022, 7:03am UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/6 "2022-06-30T07:03:57Z")
> [@sandeepkanabar](#):
>
> Because the max recommended ES heap size is 32 GB. See this - [Use more than 32GB for heap - #2 by spinscale](https://discuss.elastic.co/t/use-more-than-32gb-for-heap/204422/2). So in effect, you aren't able to fully utilise the full RAM.
That's not 100% accurate. Because the OS will cache commonly used files - by Elasticsearch - in any free memory.
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### Author:  [@sandeepkanabar](https://discuss.elastic.co/u/sandeepkanabar)
#### Post date: [June 30, 2022, 9:41am UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/7 "2022-06-30T09:41:50Z")
Ah, thanks for clarifying, Mark 👍
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 28, 2022, 9:42am UTC](https://discuss.elastic.co/t/optimizing-a-single-node-es-instance-for-throughput/307808/8 "2022-07-28T09:42:48Z")
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