On 2010/11/18 19:46, Daniel P. Berrange wrote:
> On Wed, Nov 17, 2010 at 06:19:58PM +0900, MORITA Kazutaka wrote:
>> Sheepdog is a distributed storage system for QEMU. It provides highly
>> available block level storage volumes to VMs like Amazon EBS. This
>> patch adds support for Sheepdog; we can create VMs with sheepdog
>> volumes, and attach sheepdog volumes to running machines via the
>> attach-device command.
>>
>> Sheepdog volumes can be declared like this:
>>
>> <disk type='sheepdog' device='disk'>
>> <driver name='qemu' type='raw' />
>> <source vdi='volume_name' host='hostname' port='7000'/>
>> <target dev='vda' bus='virtio' />
>> </disk>
>>
>> 'host' and 'port' in the source element are optional. If they are not
>> specified, sheepdog clients use the default value (localhost:7000).
>
> I'm not too familiar with sheepdog implementation, but I understand
> that each block device is stored across multiple hosts, but you're
> only listing one hostname here. In the proposal for supporting RBD/
> CEPH in libvirt/QEMU, there's tan option to give multiple hostnames.
> Is the need to give multiple hostnames going to be something that
> is also relevant for Sheepdog, or does it cope with this in an
> entirely different way ?
We use the hostname as like a gateway to access sheepdog volumes.
Though we could extend it to multiple hostnames to achieve high
availability, how to use these parameters as qemu arguments needs to
be discussed.
>
> As mentioned in the RBD thread[1], I'm wondering whether we should aim
> for separate 'types' for each network block device or try to merge
> them into one common syntax like
>
> <disk type="network" device="disk">
> <driver name="qemu" type="raw" />
> <source protocol='rbd|sheepdog|nbd' name="...some image identifier...">
> <host name="mon1.example.org" port="6000">
> <host name="mon2.example.org" port="6000">
> <host name="mon3.example.org" port="6000">
> </source>
> <target dev="vda" bus="virtio" />
> </disk>
Are monitor addresses necessary in the above syntax for RBD? I guess
the monitor addresses are parameters to create a rbd image, but not
ones to use a rbd image. If so, we can make the syntax a bit simpler like
<disk type="network" device="disk">
<driver name="qemu" type="raw" />
<source protocol='rbd|sheepdog|nbd' name="..." host="hostname" port="6000" />
<target dev="vda" bus="virtio" />
</disk>
Thannks,
Kazutaka
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