Bug 1395451

Summary:	vfs_cache_pressure at 50 could cause issues
Product:	[Red Hat Storage] Red Hat Storage Console	Reporter:	Alexandre Marangone <amarango>
Component:	ceph-ansible	Assignee:	Sébastien Han <shan>
Status:	CLOSED ERRATA	QA Contact:	Vidushi Mishra <vimishra>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	2	CC:	adeza, aschoen, ceph-eng-bugs, gmeno, hnallurv, jdurgin, kdreyer, nthomas, sankarshan, seb
Target Milestone:	---
Target Release:	2
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	ceph-ansible-2.2.1-1.el7scon	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-06-19 13:15:55 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Alexandre Marangone 2016-11-16 00:06:07 UTC

Description of problem:
In ceph-ansible we set vfs_cache_pressure at 50 by default. It may create issues if a storage node has a lot of memory and a lot of objects (http://tracker.ceph.com/issues/12405)

I think the reasonable thing to do would be to leave it default (100).

Comment 2 seb 2016-11-16 10:52:34 UTC

How strong is the consensus on this?

Comment 3 Ken Dreyer (Red Hat) 2017-03-03 17:18:46 UTC

Would a core dev please let us know what the optimum behavior is here for ceph-ansible?

Comment 4 Josh Durgin 2017-03-03 17:29:30 UTC

(In reply to Ken Dreyer (Red Hat) from comment #3)
> Would a core dev please let us know what the optimum behavior is here for
> ceph-ansible?

I'd recommend not setting vfs_cache_pressure in ceph-ansible. The syncfs issue is still there, and has caused real problems in the past, whereas there hasn't been good data showing lower vfs_cache_pressure is very helpful - the only cases I'm aware of have shown it makes little difference to performance.

Comment 5 Ken Dreyer (Red Hat) 2017-03-03 18:27:27 UTC

Thanks Josh, PR @ https://github.com/ceph/ceph-ansible/pull/1347

Comment 10 errata-xmlrpc 2017-06-19 13:15:55 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:1496