# Windows Defrag cause node to become unresponsive?

**URL:** <https://discuss.elastic.co/t/windows-defrag-cause-node-to-become-unresponsive/75570>\
**Category:** Elasticsearch\
**Created:** [February 17, 2017, 11:54pm UTC](https://discuss.elastic.co/t/windows-defrag-cause-node-to-become-unresponsive/75570 "2017-02-17T23:54:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jthoni](https://avatars.discourse-cdn.com/v4/letter/j/b9e5f3/32.png) [@jthoni](https://discuss.elastic.co/u/jthoni)\
**Post date:** [February 17, 2017, 11:54pm UTC](https://discuss.elastic.co/t/windows-defrag-cause-node-to-become-unresponsive/75570/1 "2017-02-17T23:54:42Z")

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I have been trying to track down an issue where we have nodes become unresponsive momentarily, causing the cluster to think they have left. I have assumed this to be a GC issue and have been trying to optimize to that end. I added a bunch of telemetry and while investigating I noticed something. I had five nodes that had network blips overnight. During this time I did not see any excessive heap use or GC. I was looking through the event viewer on the nodes and happened to notice the same error on all five nodes. It was:

> Log Name: Application  
> Source: Microsoft-Windows-Defrag  
> Date: 2/17/2017 4:27:41 AM  
> Event ID: 257  
> Task Category: None  
> Level: Error  
> Keywords: Classic  
> User: N/A  
> Computer: ocv-es-17  
> Description:  
> The volume (C:) was not optimized because an error was encountered: Neither Slab Consolidation nor Slab Analysis will run if slabs are less than 8 MB. (0x8900002D)

It would seem to be unrelated, but on all four nodes, this error preceded the node dropping off by a 3 to 5 minutes:

```
Node	Down	Up	Window	Defrag	Leadtime
es-17	4:32:36	4:33:40	0:01:04	4:27:00	0:05:36
es-12	4:42:04	4:47:16	0:05:12	4:35:00	0:07:04
es-11	4:53:21	4:55:51	0:02:30	4:51:00	0:02:21
es-13	5:11:16	5:16:21	0:05:05	5:08:00	0:03:16
es-07	1:45:56	1:46:42	0:00:46	1:42:35	0:03:21

```

I don't see any other instances of the Defrag error this week.

Is there any way that Defrag could be causing problems with Elasticsearch?

Thanks,  
~john

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [March 17, 2017, 11:55pm UTC](https://discuss.elastic.co/t/windows-defrag-cause-node-to-become-unresponsive/75570/2 "2017-03-17T23:55:29Z")

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