Optimizing Index that has grown far too large, suggested settings based on experience needed!

So I have an index that I did not expect to grow to the size it's at now, it was setup very naively. I've put off updating it long enough, time to set up a fresh cluster designed for the load! The Index has reached a total size of 1.9TB (yes I know that is awfully large.)


  • Total Size: 1.9TB
  • Documents: 5.9B
  • Current number of shards: 5
  • Index memory usage: 7.5GB
  • Indexing rate varies with average = 526/s
  • Segments: 600

Access patterns:
Query performance (for my users) is important for recent logs within the past two days. Internally, aggregate queries for the past month are used for analytics (responsiveness of these queries is less vital.)

My current thinking is to use Index Lifecycle Management:
rollover to new index after it reaches 40GB size, and retain the data for 30 days.
Tentative plan is to use a 3 node cluster and have 1 shard and 1 replica per index.

I'd love to hear if anyone has experience with a similiar load or any suggestions for shard/node settings or optimizing indexes with ILM. I've also seen some use Index aliases to setup their own daily index rollover (https://www.elastic.co/guide/en/elasticsearch/reference/5.5/indices-aliases.html), I'm leaning towards using ILM but don't have personal experience with either.

Thanks in advance for any advice you can provide!


using ILM sounds like a good plan to start, from what I read. If you only need to query the last two days, you may want to make sure that the 40gb per index results enough indices, so that you do not query far more than two days when hitting that index (given your terabyte based size that seems to be the case).

Also, one thing to keep in mind, with 40-50gb per index, you will end up with 50 indices with that amount of data, you might even increase that a little (but I'm not sure if 1.9tb is the size of your 30 day dataset).

Hope this helps as a start!


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