You can easily verify if your target supports thin-provisioning via the UNMAP command.
Download the sg3-utils package and either mount the LUN locally via the kernel open-iscsi or apply the libiscsi patch to sg3-utils to make it iscsi-aware then use the commands "sg_unmap" to try to unmap regions and "sg_get_lba_status" to check that the regions are now unmapped. On Fri, Aug 10, 2012 at 9:54 PM, Stefan Priebe - Profihost AG <s.pri...@profihost.ag> wrote: > http://www.nexenta.com/corp/products/what-is-openstorage/nexentastor > > tells me: > "SCSI UNMAP as a client-side feature frees up storage in the back end, in > the context of thin provisioning (a 100-to-one reduction in space for VDI > when using NexentaStor)." > > So i would say nexenta supports it. But i'm using virtio-scsi-pci? I'm > really sorry to ask so many questions. > > Stefan > Am 10.08.2012 13:20, schrieb ronnie sahlberg: > >> On Fri, Aug 10, 2012 at 8:30 PM, Paolo Bonzini <pbonz...@redhat.com> >> 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 >> >
