# Does "indices.segments.memory\_in\_bytes" in Node stats API show actual memory usage in OS cache?
**URL:** https://discuss.elastic.co/t/does-indices-segments-memory-in-bytes-in-node-stats-api-show-actual-memory-usage-in-os-cache/110979
**Category:** Elasticsearch
**Created:** [December 10, 2017, 6:22pm UTC](https://discuss.elastic.co/t/does-indices-segments-memory-in-bytes-in-node-stats-api-show-actual-memory-usage-in-os-cache/110979 "2017-12-10T18:22:30Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@YuWatanabe](https://discuss.elastic.co/u/YuWatanabe)
#### Post date: [December 10, 2017, 6:22pm UTC](https://discuss.elastic.co/t/does-indices-segments-memory-in-bytes-in-node-stats-api-show-actual-memory-usage-in-os-cache/110979/1 "2017-12-10T18:22:30Z")
I would like to ask question about **indices.segments.memory\_in\_bytes** in Node Stats API .
Before asking the question I have read [definitive guide](https://www.elastic.co/guide/en/elasticsearch/guide/current/near-real-time.html#near-real-time) and understood that segments are also exists in OS cache.
In my system, vmstat shows available memory is about **32 GB** (free + buffer + cache) . OS memory is 64GB.
```
2017-12-01 11:05:01 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
2017-12-01 11:05:01 r b swpd free buff cache si so bi bo in cs us sy id wa st
2017-12-01 11:05:01 19 8 602408 497496 16 31037824 0 0 388 10411 1 0 48 7 41 4 0
2017-12-01 11:06:01 5 0 602396 412732 16 31117308 0 0 2358 161207 31772 56060 44 6 46 4 0
2017-12-01 11:07:01 9 1 602396 2158624 16 29376444 0 0 2241 152205 36625 52261 47 6 42 4 0
2017-12-01 11:08:01 13 10 602380 1612348 16 29921360 8 0 5728 147693 26983 52309 48 6 42 4 0
```
Segments.memory\_in\_bytes shows about 7.6GB.
```
"segments" : {
"count" : 4757,
"memory_in_bytes" : 7654472672,
"terms_memory_in_bytes" : 5632402110,
"stored_fields_memory_in_bytes" : 1788182664,
"term_vectors_memory_in_bytes" : 0,
"norms_memory_in_bytes" : 306880,
"points_memory_in_bytes" : 213440590,
"doc_values_memory_in_bytes" : 20140428,
"index_writer_memory_in_bytes" : 116584108,
"version_map_memory_in_bytes" : 5922525,
"fixed_bit_set_memory_in_bytes" : 10688,
"max_unsafe_auto_id_timestamp" : 1512086419369,
"file_sizes" : { }
},
```
Heap is commited about **32 GB**.
```
"jvm" : {
"timestamp" : 1512095101864,
"uptime_in_millis" : 171846023,
"mem" : {
"heap_used_in_bytes" : 16159640384,
"heap_used_percent" : 50,
"heap_committed_in_bytes" : 32098877440,
```
Given the fact that segment size in memory is **7.6GB** and heap commited bytes is **32 GB** , I was expecting vmstat to show about **24.4 GB**. But its not.
Total OS memory : 64GB
Assigned Heap Size : 32 GB
Segment Size : 7.6GB
**Available memory : about 24.4 GB**
My question is , is **segment.memory\_in\_bytes** the usage in OS cache?
I appreciate if someone can give me advice.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 7, 2018, 6:23pm UTC](https://discuss.elastic.co/t/does-indices-segments-memory-in-bytes-in-node-stats-api-show-actual-memory-usage-in-os-cache/110979/2 "2018-01-07T18:23:17Z")
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