Random blocks when accessing rbd images

[Guido Winkelmann <guido-ceph@thisisnotatest.de>]

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.)

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

	Guido