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* Is using the 'discard' mount option safe on an rbd?
@ 2012-09-06 21:57 Nick Bartos
  2012-09-06 22:14 ` Josh Durgin
  0 siblings, 1 reply; 2+ messages in thread
From: Nick Bartos @ 2012-09-06 21:57 UTC (permalink / raw)
  To: ceph-devel

Is it safe to use the discard mount option when mounting a xfs
filesystem on an rbd (using the kernel driver)?  We're currently using
kernel 3.5.3 and Ceph 0.48.1.

Also, are there any stability issues doing it from a qemu VM?  It
looks like support for rbd discard was added in qemu 1.1, but I wasn't
sure how stable it was.

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: Is using the 'discard' mount option safe on an rbd?
  2012-09-06 21:57 Is using the 'discard' mount option safe on an rbd? Nick Bartos
@ 2012-09-06 22:14 ` Josh Durgin
  0 siblings, 0 replies; 2+ messages in thread
From: Josh Durgin @ 2012-09-06 22:14 UTC (permalink / raw)
  To: Nick Bartos; +Cc: ceph-devel

On 09/06/2012 02:57 PM, Nick Bartos wrote:
> Is it safe to use the discard mount option when mounting a xfs
> filesystem on an rbd (using the kernel driver)?  We're currently using
> kernel 3.5.3 and Ceph 0.48.1.

The kernel rbd driver doesn't support discard yet 
(http://tracker.newdream.net/issues/190).

> Also, are there any stability issues doing it from a qemu VM?  It
> looks like support for rbd discard was added in qemu 1.1, but I wasn't
> sure how stable it was.

There was one bug (http://tracker.newdream.net/issues/2958) whose fix
will be in the next release. Note that you need an extra qemu option
(http://tracker.newdream.net/issues/2777) for the guest to detect
discard support.

Josh

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2012-09-06 21:57 Is using the 'discard' mount option safe on an rbd? Nick Bartos
2012-09-06 22:14 ` Josh Durgin

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