# Shards Distribution in Multiple disks

**URL:** <https://discuss.elastic.co/t/shards-distribution-in-multiple-disks/121489>\
**Category:** Elasticsearch\
**Created:** [February 26, 2018, 1:07pm UTC](https://discuss.elastic.co/t/shards-distribution-in-multiple-disks/121489 "2018-02-26T13:07:29Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![loren](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/loren/32/44942_2.png) [@loren](https://discuss.elastic.co/u/loren)\
**Post date:** [February 27, 2018, 5:41pm UTC](https://discuss.elastic.co/t/shards-distribution-in-multiple-disks/121489/4 "2018-02-27T17:41:11Z")

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Correct, a single shard will only live on one disk. As for which disks get the allocation, my understanding/experience is that the allocator attempts to balance the shard count, not the disk usage. So let's say you have:

1. sda, 70% full, 10 shards
2. sdb, 10% full, 12 shards
3. sdc, 10% full, 12 shards
4. sdd, 10% full, 12 shards

If you create a new single shard index, you might think it would go to one of the 3 nearly empty disks. Instead it'll pile on to the 70% full disk, because it only has 10 shards.

Now, once that 70% full disk becomes 85% full, the default disk threshold watermark will kick in and it won't get assigned new shards.

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