- instance : 6ea
: each instance -> 16 cpu, 32GB Ram, 1TB SSD
- node : 6ea
: total indices number is 75
-> each index has only 1 shard and about 600,000 docs (2~3GB)
replica number for each index is 5 (i.e., all nodes have primary or replica shard for each index)
We have done search traffic test with the below scnearios without any indexing job on the above env.
(search request type is dfs_query_then_fetch, and disbaled query cache and requests cache)
Case 1. Send search requests to only 25 indices -> search latency : 40ms
Case 2. Send search requests to all 75 indices -> search latency : 190ms
Amount of search traffic is same, just the number of target indices for search requests is different.
But there is much difference of search latency between case 1 and 2.
We have found disk IOPS has increased much more for Case 2 and we guess it causes overhead of search latency.
Could we know why disk IOPS has increased compared with Case 1?