Re: [libvirt] [PATCH] support sheepdog volumes

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