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Re: [Qemu-devel] [PATCH v2] scsi-disk: add UNMAP limits to block limits
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From: |
Bharata B Rao |
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Subject: |
Re: [Qemu-devel] [PATCH v2] scsi-disk: add UNMAP limits to block limits VPD page |
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Date: |
Sun, 22 Dec 2013 19:56:40 +0530 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sun, Dec 22, 2013 at 02:57:27PM +0100, Paolo Bonzini wrote:
> Linux prefers WRITE SAME to UNMAP if the limits are zero, and WRITE
> SAME does not discard anything unless the device can guarantee that
> the resulting block is zero.
>
> Setting the maximum unmap block and descriptor counts to non-zero
> makes Linux choose UNMAP and fixes thin provisioning on glusterfs.
>
> While the maximum unmap block count can have some effect on performance,
> the (suggested) maximum number of descriptors is not particularly
> important so I didn't add a customization option. SCSI drivers are
> used to online firmware updates so I'm not yet adding versioning support
> for SCSI, but we're probably getting close to the point when it's worth
> thinking about it.
>
> Reported-by: Bharata B Rao <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
This patch fixes thin provisioning on gluster.
Tested-by: Bharata B Rao <address@hidden>
Regards,
Bharata.