Index has too many segments

[ihenrypan (henrypan)]

Hi, I have an index has too many segments(more than 7000).
When I restore the index from snapshot, segment number is 340(index has 170 shards). After spark-streaming write data to index in few days, the segment number is increase. As shown in the jpg:

other info:
es version: 2.3.5
index.refresh_interval: 3s
index size: about 560gb
disk:rotational disk
per shard size: about 1.6gb

Thank you!

[Christian_Dahlqvist]

If you have a slow disk it is quite possible that Elasticsearch segment merging can not keep up if you are indexing heavily. Have you followed the guidelines outlined here?

Given that you are on a very old version I would also recommend upgrading.