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From: | Stefan Priebe - Profihost AG |
Subject: | Re: [Qemu-devel] virtio-scsi vs. virtio-blk |
Date: | Fri, 10 Aug 2012 14:38:47 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0 |
never used this tool. Output is: This looks like this: # sg_unmap --lba=0x1000 --num=1 /dev/sde # sg_get_lba_status --lba=0x1000 /dev/sde get LBA status: transport: Host_status=0x10 is invalid Driver_status=0x08 [DRIVER_SENSE, SUGGEST_OK] Get LBA Status command failed try '-v' option for more information Stefan Am 10.08.2012 13:58, schrieb ronnie sahlberg:
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 <address@hidden> 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 <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
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