Re: [libvirt] Share storage using iscsi [EDIT as I cut off part]

Łukasz Mierzwa wrote: [...] > Let me make that little more clear: > 1. Lets assume I have one storage node that is acting as a iscsi target. > 2. This storage node has one big block device (RAID of some kind) that > will be used for storing virtual machines volumes > 3. I have multiple nodes for hosting virtual machines. > 4. Each of those hosting nodes needs to be able to access every volume > stored on the storage node (for live migration) using iscsi. > > I'm looking for proper way to do this. Right now I'm thinking about this > setup: > 1. On the storage node I will create lvm volume group using my RAID. > 2. Each virtual machine volume is created as lvm logical volume, it > doesn't matter how this volume is created (by hand, using management app > or any other way) but it always happens on the storage node. I could > export whole RAID as a single LUN, create lvm volume group on top of > that, but to be able to work with this lvm volume group from every > hosting node at the same time I would need to use clustered lvm (or > something like that) and that would add some complexity. > 3. Each lvm logical volume is exported as unique LUN (also out of > libvirt scope) > 4. iscsi LUNs are discovered using libvirt iscsi volume pool, and > assigned to right virtual machine. I see what you're proposing, and you're correct. If you confine the visibility of the LVs to the iSCSI target and expose each one as a separate iSCSI LUN, you don't need clvm on the nodes. That will work fine, and libvirt will handle the discovery through a refresh of the volume pool. As you point out, libvirt won't handle telling the iSCSI target to create the new LUNs. If you go the route of exposing the VG to the nodes, you would need clvm on the nodes. As a side note, I don't object to creating functionality to allow libvirt to manage iSCSI targets, extending the volume create/delete code to interface with the target. However, I don't want to try to create code to manage every possible iSCSI target. If you wanted to submit a patch to libvirt to do the kind of target management you're looking for, I would support that effort, and I'd be happy to work with you to set up a framework for plugging in code to manage whatever arrays anybody wanted to support. You're not the only person to want that functionality, and if it's done in a well-defined way, I think it would be a good thing. Others on the list might have different opinions.