On Fri, Aug 10, 2012 at 8:30 PM, Paolo Bonzini <address@hidden> wrote:
Il 10/08/2012 12:28, Stefan Priebe - Profihost AG ha scritto:
I'm using iscsi. So no raw or qcow2.
Ok, then you need to use scsi-block as your device instead of scsi-disk
or scsi-hd. This will disable the QEMU SCSI emulation and let your VM
talk directly to the NAS.
CCing Ronnie who may be interested in bug reports since I'm on holiday
starting "soon".
I think it works on any,
You can of course not boot from a if=scsi disk in qemu,
but any '-drive file=iscsi://...,if=scsi' should work as long as it is
not the boot device.
SCSI emulation in qemu picks this up via WRITESAME10/16 and then calls
bdrv_aio_discard()
block/iscsi.c is invoked for discard and then translates this back to
a SBC UNMAP command it sends to the target.
Now, block/iscsi.c does assume that any target that reports that it
supports thin-provisioning actually implements UNMAP command.
There could be targets that support thin-provision ing that does NOT
support UNMAP and unly support discard via WRITESAME10/16
so at some stage I should send a patch to iscsi.c to check which
commands the target supprots and use one of the supported ones instead
of a blanket
"you say you support thin-provisioning, I take that as confirmation
you support SBC UNMAP"
regards
ronnie sahlberg