# ILMs in cluster not performing rollover when conditions are met

**URL:** <https://discuss.elastic.co/t/ilms-in-cluster-not-performing-rollover-when-conditions-are-met/383369>\
**Category:** Elasticsearch\
**Tags:** ilm-index-lifecycle-management\
**Created:** [November 11, 2025, 3:23pm UTC](https://discuss.elastic.co/t/ilms-in-cluster-not-performing-rollover-when-conditions-are-met/383369 "2025-11-11T15:23:11Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [November 17, 2025, 6:12pm UTC](https://discuss.elastic.co/t/ilms-in-cluster-not-performing-rollover-when-conditions-are-met/383369/5 "2025-11-17T18:12:36Z")

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> [@Natalia\_Mellino](#):
>
> Now all shards are around 50gb which seems ok, but a few days ago for one of the shards I got 56gb

All segments in Elasticsearch are immutable, so when merging takes place new merged segments need to be created before old, redundant ones can be deleted. This will lead to the reported shard size fluctuating over time like you captured here. I believe ILM do not just look at the raw current shard size (which would frequently be affected by merging) but instead estimates the merged size.

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