# Disk usage threshold **URL:** \ **Category:** Elasticsearch\ **Created:** [June 29, 2021, 9:22am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328 "2021-06-29T09:22:30Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Abhishek\_Shinde](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@Abhishek\_Shinde](https://discuss.elastic.co/u/Abhishek_Shinde)\ **Post date:** [June 29, 2021, 9:22am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/1 "2021-06-29T09:22:30Z")
I'm planning integrate Elasticsearch as a single node cluster per application server. Application server is getting hosted in customer environment. For disk threshold, I'm planning to use only disk flood\_stage configuration as low and high watermark will have no impact. I know the default flood stage is set to 95% but would like to know the consequences of keeping it at 99% by default? ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [July 1, 2021, 2:03am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/2 "2021-07-01T02:03:35Z")
That depends on how large the disk is and what your use case is. If you are talking a 4TB drive that Elasticsearch can use, then 99% leaves 41GB to work with. That's not a lot if Elasticsearch needs to merge a large index. ---
**Author:** ![Abhishek\_Shinde](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@Abhishek\_Shinde](https://discuss.elastic.co/u/Abhishek_Shinde)\ **Post date:** [July 3, 2021, 6:43pm UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/3 "2021-07-03T18:43:19Z")
Our typical use case at customer end is 2TB. I wanted dig down the use cases in which will be needed of space? One of the reason that I could think of is disk expansion as elastic support only single path per node. Could please elaborate the merge index use case with some references? ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [July 5, 2021, 2:03am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/4 "2021-07-05T02:03:09Z")
The underlying Lucene segments of an index will merge over time. So if you have 2 segments that are (eg) 5 gig, then you need `5 x 2` _plus_ another 10 gig for the merge to happen in, until the merge is completed and then the original segments are deleted. ---
**Author:** ![Abhishek\_Shinde](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@Abhishek\_Shinde](https://discuss.elastic.co/u/Abhishek_Shinde)\ **Post date:** [July 5, 2021, 6:06am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/5 "2021-07-05T06:06:53Z")
Thanks for this explanation. We will be having shard of 50 GB each which would be heavily ingested with user email data. I would like to what is the default segment size, how frequently segments are getting merged, is there any max segment merge threshold parameter? ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [July 6, 2021, 1:35am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/6 "2021-07-06T01:35:29Z")
There is no default segment size and you cannot limit the size of a segment, Elasticsearch handles things transparently. [Merge | Elasticsearch Guide [7.13] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/7.13/index-modules-merge.html) has some info on this. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [August 3, 2021, 1:35am UTC](https://discuss.elastic.co/t/disk-usage-threshold/277328/7 "2021-08-03T01:35:31Z")
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