Re: Random blocks when accessing rbd images

[Wido den Hollander <wido@widodh.nl>]

Hi,

On 12/15/2011 04:07 PM, Guido Winkelmann wrote:
> Hi,
>
> I've got a small ceph cluster with one mon, one mds and two osds (all on the
> same machine, for now), that I want to use as a block- and file storage backend
> for qemu machine virtualisation.
>
> I found that read access to some of the rbd images, or parts of some of them
> sometimes blocks indefinitely, usually after the image has been sitting around
> untouched for a while, for example over night. This has the effect that virtual
> machines that try to access their disks as well as rbd commands like "rbd cp"
> will just hang indefinitely.
>
>   I found that these blocks can usually be "fixed" by restarting one of the
> osds.
>
> The last time this happened, ceph -s reported one of the osds to be in state
> "active+clean+scrubbing". (I'm afraid I don't have the complete output from
> ceph -s anymore.)

I've been seeing the exact same behaviour, but I wasn't able yet to get 
into it a bit deeper.

As far as I know, when a PG gets scrubbed it become unavailable for a 
short period, but since this scrub blocks/loops the PG will never become 
available again, thus blocking the virtual machine.

I saw this behaviour with v0.37 and 0.38, upgrading to 0.39 to see if it 
still exists.

Wido

>
> Does anybody have any idea what could be going wrong here?
>
> 	Guido
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