Re: TRIM vs UNMAP vs WRITE SAME and thin devices

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Matthew Wilcox wrote:
On Sun, Feb 08, 2009 at 03:06:44PM -0500, Greg Freemyer wrote:
I found a list of T10 activities just since just Dec. 1, 2008 and it
is a bit overwhelming.  (ie. 08-356r4 is but one of many recent
reports)

http://www.t10.org/new_a.htm

For those of us that don't live and breath the SCSI spec, is there an
overview site describing what is going on.

I've been working off 08-149r7.pdf.  I'm sure that's been superseded by
now.
08-356r4 	SBC-3: WRITE SAME unmap bit 	David L. Black 	PDF (56608)	2008/12/10

Probably interesting.  Haven't read it myself.

This is only a four page proposal - basically, we would use the write same command with a special unmap bit set to tell the target that it may (at its option) unmap the blocks. If not, it would in fact have to set the data to the indicated pattern in the command which I presume would be all zeros in the normal case.
08-356r5 	SBC-3 Thin Provisioning Commands 	Fred Knight, David L.
Black 	PDF (387549)	2009/01/15

Fred Knight seems to be the main coordinator of this effort, so yes.

Fred and David Black both have been quite active.
08-149r7 	SBC - Thin Provisioning 	Frederick Knight 	PDF (281001)	2008/12/08

That's the one I'm working from.

08-149r8 	SBC - Thin Provisioning 	Frederick Knight 	PDF (281387)	2009/01/09

A newer version ... thought so.

09-011r1 	SBC-3 Thin Provisioning Threshold Notification 	Frederick
Knight 	PDF (32757)	2009/01/09

Clearly related.

08-149r9 	SBC - Thin Provisioning 	Frederick Knight 	PDF (353888)	2009/01/15

Even newer version of what I've been working from.

09-012r0 	Minutes: CAP - Thin Provisioning 12/4 con-call 	Frederick
Knight 	PDF (38063)	2008/12/08

Probably tedious.

08-396r3 	SPC-4: Reporting support for all DIF types 	George Penokie
	PDF (85358)	2009/01/14

Unrelated, I would think.

I'd go with 08-149r9 to get a good overview.


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