[pve-devel] scsi-hd vs scsi-generic with iSCSI

[Daniel Berteaud]

----- Le 8 Oct 19, à 12:28, Thomas Lamprecht t.lamprecht at proxmox.com a écrit :

> 
> Thanks for the nice write up and clear reproducer!
> 
> It seems that if we cannot use the same backend for all disks we need to
> die when a disk move to a storage backend is request, and that move would
> need to change the scsi "backend".
> As I'd not like to die it would be better to see if there's still the need
> for different backends.

Dying wouldn't be very nice indeed (I need to be able to move disks between NFS and ZFS over iSCSI on a regular basis) 

If scsi-hd was always selected, there would be no issue. I've patched my QemuServer.pm to do that for now.
Not sure if scsi-generic/scsi-block has any advantages, but I couldn't measure performance diff in my case. unmap is also passed correctly with scsi-hd. IMHO, unless there are strong values with them (which I'am unaware off, but I couldn't find any documentation about all those backends), we should always use scsi-hd, as it's working with all storage types and allows live disk move from any storage type to any other, including the issue I have specific to ZFS over iSCSI (guest I/O error during live move from ZFS over iSCSI to something else)


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