[ovirt-devel] Access to images in block domain from more VMs

Hi, we have a large gap in handling ISO files in data domains and especially on block domains. None of the flows that work with ISOs works (well, one sort of does): 1) Change CD for running VM [1] 2) Attaching boot disk in Run Once -- this works but I wonder if it's by accident, because engine issues spurious teardown on images [2] 3) Guest tools during VM import [3] 4) Automatic attach of guest tools to Windows VMs Before virt can fix all those we need input from storage on how we should handle the images on block domains. The specialty of ISO image is that it makes sense to have it attached to multiple VMs. And that also means something should control whether image needs attaching or whether the image is already attached to the host. Similarly the image should be (attempted to) detached only when there is no longer any VM on the host that uses it. Hence my question to storage -- is there already some framework from storage for handling this? Does it make more sense to do this on engine side or should each host handle it on it's own? To me it seems preferable to handle this on engine side as that is where the requests for attach/detach normally come from (disks in VM import are an exception). It could possibly mean less race conditions (but I may be totally wrong here). Also having it on VDSM side would probably mean changes to the API for 1) and 2). Any input appreciated. Tomas [1] https://bugzilla.redhat.com/show_bug.cgi?id=1589763 [2] https://bugzilla.redhat.com/show_bug.cgi?id=1721455 [3] https://bugzilla.redhat.com/show_bug.cgi?id=1721455 -- Tomáš Golembiovský <tgolembi(a)redhat.com&gt;