[Sheepdog] qemu-img convert slowness and high availability status

krimson krims0n32 at gmail.com
Tue Jun 14 21:35:51 CEST 2011

time qemu-img convert /dev/vmvg/web /home/spja/ff

real    2m12.866s
user    0m0.680s
sys    0m11.950s

quite the difference :)

I ran into another issue now, after killing the sheep daemon on one of 
the clusternodes it seems sheepdog is unable to form a cluster anymore:
sheep: get_cluster_status(408) sheepdog is waiting with newer epoch, 1 3

whereas the other node says "older epoch" instead of "newer epoch". How 
can I resolve this without losing the VDI's in the sheepstore ?

Thanks !

On 06/14/2011 06:05 PM, MORITA Kazutaka wrote:
> At Mon, 13 Jun 2011 23:35:32 +0200,
> krimson wrote:
>> Hi again :)
>> I was converting an LVM based image to sheepdog using:
>> # qemu-img convert /dev/vmvg/web sheepdog:web
>> and noticed it took 2.5 hours to complete. The image is 8GB in size. The
>> sheepdog/corosync network is a direct Gbit link between two nodes. Any
>> idea as to why this is taking so long ? Small blocksize perhaps ? The
>> cluster is using copies=2. Using sheepdog from git (0.2.3) and qemu-kvm
>> 0.14.
> How long does it take when you convert the image to a raw image on
> LVM?
>   $ time qemu-img convert /dev/vmvg/web /your_store_directory/web.raw
> This should show an ideal time for converting to Sheepdog images on
> your machine.
>> Another question regarding the state of high availability in sheepdog, I
>> noticed it is possible to specify multiple sheepdog hosts in my qemu XML
>> definition, and it defaults to localhost.
> Sheepdog accepts only one host in the XML format.  See also
> http://libvirt.org/formatdomain.html#elementsDisks
>> I would like to avoid
>> specifying multiple sheepdog hosts in the XML definition if possible and
>> was wondering what happens to the VMs when the sheep daemon dies for
>> example. The entire node failing would not be a problem I guess as the
>> remaining node would then startup the VMs that were running on the
>> failed node.
> Unfortunately, there is no automatic connection failover support
> because Sheepdog assumes that VMs connect to localhost (the failure of
> localhost means that VMs cannot survive any more).
> We have a plan to remove this restriction in future, but currently
> Sheepdog cannot handle the failure.
> Thanks,
> Kazutaka

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