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Re: [Qemu-devel] [PATCH] sheepdog: implement SD_OP_FLUSH_VDI operation
From: |
MORITA Kazutaka |
Subject: |
Re: [Qemu-devel] [PATCH] sheepdog: implement SD_OP_FLUSH_VDI operation |
Date: |
Fri, 20 Apr 2012 12:15:36 -0700 |
User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) LIMIT/1.14.10 (Furuichi) APEL/10.8 Emacs/22.1 (mac-apple-darwin) MULE/5.0 (SAKAKI) |
At Fri, 20 Apr 2012 20:05:48 +0200,
Christoph Hellwig wrote:
>
> On Tue, Apr 03, 2012 at 01:35:50AM +0800, Liu Yuan wrote:
> > From: Liu Yuan <address@hidden>
> >
> > Flush operation is supposed to flush the write-back cache of
> > sheepdog cluster.
> >
> > By issuing flush operation, we can assure the Guest of data
> > reaching the sheepdog cluster storage.
>
> How does qemu know that the cache might need flushing in the backend?
>
> If the backend expects a flush we need to make sure one is sent after
> every write if the user selects cache=writethrough or cache=directsync.
> Given how expensive that is you should also consider adding an equivalent
> to the FUA flag for writes in that case, or simply allow the qemu driver
> to tell the cluster that it needs to operate in writethrough mode for
> this VDI.
His patch sets the SD_FLAG_CMD_CACHE flag for writes only when the
user selects cache=writeback or cache=none. If SD_FLAG_CMD_CACHE is
not set in the request, Sheepdog servers are forced to flush the cache
like FUA commands.
Thanks,
Kazutaka
- Re: [Qemu-devel] [PATCH v3] sheepdog: implement SD_OP_FLUSH_VDI operation, (continued)
- Re: [Qemu-devel] [PATCH v3] sheepdog: implement SD_OP_FLUSH_VDI operation, MORITA Kazutaka, 2012/04/03
- [Qemu-devel] [PATCH v4] sheepdog: implement SD_OP_FLUSH_VDI operation, Liu Yuan, 2012/04/03
- [Qemu-devel] [PATCH v4 UPDATE] sheepdog: implement SD_OP_FLUSH_VDI operation, Liu Yuan, 2012/04/03
- Re: [Qemu-devel] [PATCH v4 UPDATE] sheepdog: implement SD_OP_FLUSH_VDI operation, MORITA Kazutaka, 2012/04/03
- Re: [Qemu-devel] [PATCH v4 UPDATE] sheepdog: implement SD_OP_FLUSH_VDI operation, Kevin Wolf, 2012/04/03
- [Qemu-devel] [PATCH v5] sheepdog: implement SD_OP_FLUSH_VDI operation, Liu Yuan, 2012/04/03
- Re: [Qemu-devel] [PATCH v5] sheepdog: implement SD_OP_FLUSH_VDI operation, Kevin Wolf, 2012/04/04
- Re: [Qemu-devel] [PATCH v5] sheepdog: implement SD_OP_FLUSH_VDI operation, Liu Yuan, 2012/04/04
- Re: [Qemu-devel] [PATCH v5] sheepdog: implement SD_OP_FLUSH_VDI operation, Kevin Wolf, 2012/04/04
Re: [Qemu-devel] [PATCH] sheepdog: implement SD_OP_FLUSH_VDI operation, Christoph Hellwig, 2012/04/20
- Re: [Qemu-devel] [PATCH] sheepdog: implement SD_OP_FLUSH_VDI operation,
MORITA Kazutaka <=