Did you set read/write permissions to the cache pool? For example, in
openstack i need to set read/write permission for cinder to be able to use
the cache pool.
On 3 Feb 2016 17:25, "Udo Waechter" <r...@zoide.net> wrote:

> Hello,
>
> I am experimenting with adding a SSD-Cache tier to my existing Ceph
> 0.94.5 Cluster.
>
> Currently I have:
> 10 OSDs on 5 hosts (spinning disks).
> 2 OSDs on 1 host (SSDs)
>
> I have followed the cache tier docs:
> http://docs.ceph.com/docs/master/rados/operations/cache-tiering/
>
> 1st I created a new (spinning pool) and set up the SSDs as a cache tier.
> All is fine. I can create/access images with rbd.
> I can seed that it is used with "rados -p cache-pool ls"
>
>
> Now, when I add a cache pool to my existing pools, for example the one
> which hosts all my VM images all hell breaks loose.
>
> The VMs all get I/O end request errors and remount their filesystems R/O.
> If I shut them down and try to start them again, they won't start, virsh
> gives me an error  "cannot read metadata header" (or something like that).
>
> Also, "rados -p cache-pool ls" hangs forewer.
>
> I have read here:
>
> https://software.intel.com/en-us/blogs/2015/03/03/ceph-cache-tiering-introduction
> that adding caches works on-the-fly.
>
> Is there a special trick to add cache to a running, pool under load
> (which is not very high, though)?
>
> And what about the "osd tier add-cache <poolname> <poolname> <int>"
> command? its supposed to add a cache to the 1st pool. I can't see this
> be used in bost of the above links.
>
> Thanks very much,
> udo.
>
>
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>
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