TRIM vs UNMAP vs WRITE SAME and thin devices

[Ric Wheeler]

I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

One note on the SCSI devices, there was a T10 proposal to add an "UNMAP"
bit to the "WRITE SAME" command for SCSI. The details of the proposed
interface are at:

http://www.t11.org/t10/document.08/08-356r4.pdf

The up side of using WRITE SAME with unmap is that there are no fuzzy
semantics about what the unmapped sectors will be - they will all be
whatever the WRITE SAME command would have set (usually zeroes I assume).

The summary of write same is that you send down one sector (say 512
bytes of zeroes) and a count so you can do a zeroing of the target
without having to send all of the data over the wire. Very useful for
initializing members of a RAID device for example to a known pattern.

The down side would be that if we incorrectly send down a WRITE SAME
command to a non-thin device, I think that we would kick off a potential
extremely long IO. For example, imagine doing a write same of a full TB
- that could take an hour which might be an issue :-) Of course, we
should not be doing that if we get the code right.

I don't see another of the PDF's claims of advantages for file systems
to be really all that useful.

With either the write same and its proposed unmap bit or with the
original T10 unmap, do we have a short list of infrastructure that needs
fleshed out? Anything we can do to help get peoples patches to test with
their non-GA thin enabled devices?

Is there a similar short list of things to be done for T13 devices with
TRIM? Anyone have a chance to test on real hardware yet?

Thanks!

Ric

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[James Bottomley]

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

With my LSF hat on, a certain array vendor might be sponsoring to get
the opportunity to raise this issue more fully. The impression (mostly
correct) is that we're thinking about trim/unmap purely from the SSD FTL
point of view and perhaps not being as useful as we might to virtually
provisioned LUNs ... so you could mention to the other vendors that they
might have an interest in coming (and even possibly sponsoring).

Post by Ric Wheeler
My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

With no devices it's a bit hard. Also we need at least three pieces for
SSDs: Devices supporting trim, the T13 implementation of TRIM and the
SAT for UNMAP. We can get the latter two out of the proposals, but it's
still a bit of a moving target.

Post by Ric Wheeler
One note on the SCSI devices, there was a T10 proposal to add an "UNMAP"
bit to the "WRITE SAME" command for SCSI. The details of the proposed
http://www.t11.org/t10/document.08/08-356r4.pdf
The up side of using WRITE SAME with unmap is that there are no fuzzy
semantics about what the unmapped sectors will be - they will all be
whatever the WRITE SAME command would have set (usually zeroes I assume).
The summary of write same is that you send down one sector (say 512
bytes of zeroes) and a count so you can do a zeroing of the target
without having to send all of the data over the wire. Very useful for
initializing members of a RAID device for example to a known pattern.
The down side would be that if we incorrectly send down a WRITE SAME
command to a non-thin device, I think that we would kick off a potential
extremely long IO. For example, imagine doing a write same of a full TB
- that could take an hour which might be an issue :-) Of course, we
should not be doing that if we get the code right.

As I read it, non thin provisioned devices can be identified (and may
not even accept WRITE SAME).

Post by Ric Wheeler
I don't see another of the PDF's claims of advantages for file systems
to be really all that useful.
With either the write same and its proposed unmap bit or with the
original T10 unmap, do we have a short list of infrastructure that needs
fleshed out? Anything we can do to help get peoples patches to test with
their non-GA thin enabled devices?

Yes, REQ_DISCARD simply isn't broad enough to cope with all the
potential uses of WRITE SAME. If it's just a mechanism to get known
data into a discard sector, fine, we can set that at the lower level.
However, WRITE SAME has uses beyond TRIM in that it can be used as an
engine for data deduplication. If vendors are thinking of doing this,
then REQ_DISCARD isn't flexible enough.

Post by Ric Wheeler
Is there a similar short list of things to be done for T13 devices with
TRIM? Anyone have a chance to test on real hardware yet?

Not that I know of yet. It's all sort of on hold until actual devices
become available.

James


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[Ric Wheeler]

Post by James Bottomley

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

With my LSF hat on, a certain array vendor might be sponsoring to get
the opportunity to raise this issue more fully. The impression (mostly
correct) is that we're thinking about trim/unmap purely from the SSD FTL
point of view and perhaps not being as useful as we might to virtually
provisioned LUNs ... so you could mention to the other vendors that they
might have an interest in coming (and even possibly sponsoring).

That is probably worth bringing up - I don't see this as a large project
and should be reasonably quick to get completed given all the work that
David and others have already put into it. If you (with you LF hat on
:-)) have a standard form or offer process, you might want to poke at
NetApp, EMC, Hitachi, IBM, HP and Dell. We both know the names of some
people in storage in a few of those companies, others I have less
contacts with.

On the other hand, this might also be an opportunity to get them and
their engineers on the array side more directly and personally involved.

Post by James Bottomley

Post by Ric Wheeler
My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

With no devices it's a bit hard. Also we need at least three pieces for
SSDs: Devices supporting trim, the T13 implementation of TRIM and the
SAT for UNMAP. We can get the latter two out of the proposals, but it's
still a bit of a moving target.

I think that it has settled a bit - do we have a good sense of the
status of the various proposals in T13 and T10?

Post by James Bottomley

Post by Ric Wheeler
One note on the SCSI devices, there was a T10 proposal to add an "UNMAP"
bit to the "WRITE SAME" command for SCSI. The details of the proposed
http://www.t11.org/t10/document.08/08-356r4.pdf
The up side of using WRITE SAME with unmap is that there are no fuzzy
semantics about what the unmapped sectors will be - they will all be
whatever the WRITE SAME command would have set (usually zeroes I assume).
The summary of write same is that you send down one sector (say 512
bytes of zeroes) and a count so you can do a zeroing of the target
without having to send all of the data over the wire. Very useful for
initializing members of a RAID device for example to a known pattern.
The down side would be that if we incorrectly send down a WRITE SAME
command to a non-thin device, I think that we would kick off a potential
extremely long IO. For example, imagine doing a write same of a full TB
- that could take an hour which might be an issue :-) Of course, we
should not be doing that if we get the code right.

As I read it, non thin provisioned devices can be identified (and may
not even accept WRITE SAME).

I agree that the intersection of write same and thin devices is not
going to be 100%. We might end up needing both for SCSI in the worst
case I suppose.

Post by James Bottomley

Post by Ric Wheeler
I don't see another of the PDF's claims of advantages for file systems
to be really all that useful.
With either the write same and its proposed unmap bit or with the
original T10 unmap, do we have a short list of infrastructure that needs
fleshed out? Anything we can do to help get peoples patches to test with
their non-GA thin enabled devices?

Yes, REQ_DISCARD simply isn't broad enough to cope with all the
potential uses of WRITE SAME. If it's just a mechanism to get known
data into a discard sector, fine, we can set that at the lower level.
However, WRITE SAME has uses beyond TRIM in that it can be used as an
engine for data deduplication. If vendors are thinking of doing this,
then REQ_DISCARD isn't flexible enough.

I am more interested personally in the sparse support. On the dedup
side, I think that most implementations do not rely on write same. They
tend to compute hashes on the various blocks and so on.

Post by James Bottomley

Post by Ric Wheeler
Is there a similar short list of things to be done for T13 devices with
TRIM? Anyone have a chance to test on real hardware yet?

Not that I know of yet. It's all sort of on hold until actual devices
become available.
James

The vendors certainly have things that they could try in their labs if
we can get bits and pieces together for them to test with. We will need
to avoid the chicken and egg scenario where they wait for us and we wait
for them :-)

Ric

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[Eyal Shani]

Adding my 5 cents.

T13 added Trim to the latest ATA8 proposal.
http://www.t13.org/Documents/UploadedDocuments/docs2009/d2015r1-ATAATAPI_Command_Set_-_2_ACS-2.pdf

This is after the changes put into the definition, with 'Deterministic Read after Trim'.
This is not STANDARDIZED, but pretty much excepted by all sides.

I was hoping that would settle the differences between T10/T13 on this - little did I know...

We are working with David W. on his implementation for Trim feature, and hope to get to the bottom of debug process soon.
Hope to update soon...


Regards,
Eyal Shani.
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[Greg Freemyer]

Post by Eyal Shani
Adding my 5 cents.
T13 added Trim to the latest ATA8 proposal.
http://www.t13.org/Documents/UploadedDocuments/docs2009/d2015r1-ATAATAPI_Command_Set_-_2_ACS-2.pdf
This is after the changes put into the definition, with 'Deterministic Read after Trim'.
This is not STANDARDIZED, but pretty much excepted by all sides.
I was hoping that would settle the differences between T10/T13 on this - little did I know...
We are working with David W. on his implementation for Trim feature, and hope to get to the bottom of debug process soon.
Hope to update soon...
Regards,
Eyal Shani.

FYI:

Several of you remember I've been concerned about the lack of
"audit-ability" associated with the new Trim feature as relates to the
T13 spec.

I finally found a contact that is on the T-13 committee and have
expressed my concern. He said the issue was raised at a recent
meeting of the committee and that a sub-group was tasked with making a
recommendation. He said that he understands my concern and said he
would push to ensure that some sort of "reliable data" flag be in the
eventual spec.

Obviously he is just one person, so no guarantees, but I am happy to
have finally connected with someone on the committee.

Greg
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[Mark Lord]

..

Post by Eyal Shani
Adding my 5 cents.
T13 added Trim to the latest ATA8 proposal.
http://www.t13.org/Documents/UploadedDocuments/docs2009/d2015r1-ATAATAPI_Command_Set_-_2_ACS-2.pdf

..

Note that there is also a Rev.1a edition, same link as above
except change the d2015r1 to d2015r1a:

http://www.t13.org/Documents/UploadedDocuments/docs2009/d2015r1a-ATAATAPI_Command_Set_-_2_ACS-2.pdf
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[Matthew Wilcox]

Post by James Bottomley

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

With my LSF hat on, a certain array vendor might be sponsoring to get
the opportunity to raise this issue more fully. The impression (mostly
correct) is that we're thinking about trim/unmap purely from the SSD FTL
point of view and perhaps not being as useful as we might to virtually
provisioned LUNs ... so you could mention to the other vendors that they
might have an interest in coming (and even possibly sponsoring).

I thought we had agreed on a plan which satisfied the SSD and insane
array vendors. That is that we would do no tracking of allocation units
in the filesystem, but instead extend each trim out to cover the maximum
possible size. I've confirmed with Intel's SSD people that this would
cause them no harm at all (trimming already trimmed sectors won't even
cause a slowdown). Whether the filesystem people have taken note of
this, I have no idea.

[James Bottomley]

Post by Matthew Wilcox

Post by James Bottomley

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

With my LSF hat on, a certain array vendor might be sponsoring to get
the opportunity to raise this issue more fully. The impression (mostly
correct) is that we're thinking about trim/unmap purely from the SSD FTL
point of view and perhaps not being as useful as we might to virtually
provisioned LUNs ... so you could mention to the other vendors that they
might have an interest in coming (and even possibly sponsoring).

I thought we had agreed on a plan which satisfied the SSD and insane
array vendors.

I don't think we got any input from array vendors, so it's rather hard
to claim this. So part of this idea would be gathering the necessary
inputs.

Post by Matthew Wilcox
That is that we would do no tracking of allocation units
in the filesystem, but instead extend each trim out to cover the maximum
possible size. I've confirmed with Intel's SSD people that this would
cause them no harm at all (trimming already trimmed sectors won't even
cause a slowdown). Whether the filesystem people have taken note of
this, I have no idea.

It's one idea, but absent requirements from array vendors, we don't
really know if it's the right one.

James


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[Ric Wheeler]

Post by Matthew Wilcox

Post by James Bottomley

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.

With my LSF hat on, a certain array vendor might be sponsoring to get
the opportunity to raise this issue more fully. The impression (mostly
correct) is that we're thinking about trim/unmap purely from the SSD FTL
point of view and perhaps not being as useful as we might to virtually
provisioned LUNs ... so you could mention to the other vendors that they
might have an interest in coming (and even possibly sponsoring).

I thought we had agreed on a plan which satisfied the SSD and insane
array vendors. That is that we would do no tracking of allocation units
in the filesystem, but instead extend each trim out to cover the maximum
possible size. I've confirmed with Intel's SSD people that this would
cause them no harm at all (trimming already trimmed sectors won't even
cause a slowdown). Whether the filesystem people have taken note of
this, I have no idea.

That should be helpful for the array people, but for some of them with
really large delete chuck sizes, they will still miss a lot since their
size is larger than the average file size :-) I guess that we could do
something to resync - Ted mentioned some ideas for ext4.

On another note, they are pondering either using write same with the
discard bit set or the unmap command. It would seem that for thin
provisioning alone, either would work.

ric

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[Matthew Wilcox]

Post by Ric Wheeler

Post by Matthew Wilcox
I thought we had agreed on a plan which satisfied the SSD and insane
array vendors. That is that we would do no tracking of allocation units
in the filesystem, but instead extend each trim out to cover the maximum
possible size. I've confirmed with Intel's SSD people that this would
cause them no harm at all (trimming already trimmed sectors won't even
cause a slowdown). Whether the filesystem people have taken note of
this, I have no idea.

That should be helpful for the array people, but for some of them with
really large delete chuck sizes, they will still miss a lot since their
size is larger than the average file size :-) I guess that we could do
something to resync - Ted mentioned some ideas for ext4.

I'm not sure I communicated the plan effectively.

Let's consider deleting a 4k file.

The DISCARD that the filesystem sends down does not just cover the 4k
of data. It covers all adjacent free space to that 4k of data, so it
might end up sending a DISCARD of several megabytes or even gigabytes,
assuming there's that much contiguous free space.

Now, filesystems which fragment their free space will not do well on
thin provisioned devices, but then they won't do well on any devices --
keeping your free space compacted is an essential part of any filesystem's
job, even on SSDs.

[Ric Wheeler]

Post by Matthew Wilcox

Post by Ric Wheeler

Post by Matthew Wilcox
I thought we had agreed on a plan which satisfied the SSD and insane
array vendors. That is that we would do no tracking of allocation units
in the filesystem, but instead extend each trim out to cover the maximum
possible size. I've confirmed with Intel's SSD people that this would
cause them no harm at all (trimming already trimmed sectors won't even
cause a slowdown). Whether the filesystem people have taken note of
this, I have no idea.

That should be helpful for the array people, but for some of them with
really large delete chuck sizes, they will still miss a lot since their
size is larger than the average file size :-) I guess that we could do
something to resync - Ted mentioned some ideas for ext4.

I'm not sure I communicated the plan effectively.
Let's consider deleting a 4k file.
The DISCARD that the filesystem sends down does not just cover the 4k
of data. It covers all adjacent free space to that 4k of data, so it
might end up sending a DISCARD of several megabytes or even gigabytes,
assuming there's that much contiguous free space.
Now, filesystems which fragment their free space will not do well on
thin provisioned devices, but then they won't do well on any devices --
keeping your free space compacted is an essential part of any filesystem's
job, even on SSDs.

Thanks - that does sound like it will in fact help clean up. I suppose
the worst case would be deleting lots of non-contiguous small files from
a full file system (say every other 4KB or something obscure like that).

I will see what the vendors I know have come up with, I think that this
should give them something interesting to play with....

Ric


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[Matthew Wilcox]

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.
My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

Bearing in mind that I'm now three weeks behind on email, you might want
to look at
http://git.kernel.org/?p=linux/kernel/git/willy/ssd.git;a=shortlog;h=trim-20081231
which has at least one known bug (fixed by Dave Woodhouse and Ben
Herrenschmidt). I'll be able to give a more coherent answer in a few
days. Or maybe Dave will beat me to it ;-)

[Jeff Garzik]

Post by Matthew Wilcox

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.
My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

Bearing in mind that I'm now three weeks behind on email, you might want
to look at
http://git.kernel.org/?p=linux/kernel/git/willy/ssd.git;a=shortlog;h=trim-20081231
which has at least one known bug (fixed by Dave Woodhouse and Ben
Herrenschmidt). I'll be able to give a more coherent answer in a few
days. Or maybe Dave will beat me to it ;-)

BTW when will somebody send me the 4k sector patches? :)

Jeff



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[Matthew Wilcox]

Post by Jeff Garzik
BTW when will somebody send me the 4k sector patches? :)

I'll get to that on Monday; just arrived back from holiday today.

[David Woodhouse]

Post by Matthew Wilcox

Post by Ric Wheeler
I have been poked at by some vendors about the status of our support for
the virtually/thinly provisioned luns since they are getting close to
being able to test with real devices.
My quick summary is that we most of the work so far has been done
without any real hardware to play with - in 2.6.29-rc3, I don't see any
low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD
into the specific ATA or SCSI commands. Did I miss something & if not,
do we have plans to push anything upstream soonish?

Bearing in mind that I'm now three weeks behind on email, you might want
to look at
http://git.kernel.org/?p=linux/kernel/git/willy/ssd.git;a=shortlog;h=trim-20081231
which has at least one known bug (fixed by Dave Woodhouse and Ben
Herrenschmidt). I'll be able to give a more coherent answer in a few
days. Or maybe Dave will beat me to it ;-)

Ben's suggestion was that the IDE core wouldn't be sending the payload of
the command because it looks at the R/W bit... which is clear (read) in
our discard requests ATM. Making them appear to be writes is simple enough
though. I gave an updated test kernel to the Sandisk folks but haven't got
results back from them yet.

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[Greg Freemyer]

I have been poked at by some vendors about the status of our support for the
virtually/thinly provisioned luns since they are getting close to being able
to test with real devices.

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.

Maybe:
09-059r0 T10 Project Summary - January 2009 John Lohmeyer PDF
(34729) 2009/01/22
http://www.t10.org/cgi-bin/ac.pl?t=d&f=09-059r0.pdf

I have not read any of the Post Dec. 1 stuff including the above
project summary, but based on the names these seem potentially
relevant:

09-055r0 T13 Liaison Report January 09 Dan Colegrove PDF (4770) 2009/01/15

08-356r4 SBC-3: WRITE SAME unmap bit David L. Black PDF (56608) 2008/12/10

08-356r5 SBC-3 Thin Provisioning Commands Fred Knight, David L.
Black PDF (387549) 2009/01/15

08-149r7 SBC - Thin Provisioning Frederick Knight PDF (281001) 2008/12/08

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

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

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

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

09-011r0 SBC-3 Thin Provisioning Threshold Notification Frederick
Knight PDF (48523) 2008/12/08

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

09-058r0 Agenda for T10 Meeting #90 March 2009 John Lohmeyer PDF
(61437) 2009/01/19

09-020r0 T11 Liaison Report, December 2008 Robert Snively PDF
(13117) 2008/12/19

09-032r0 Minutes of T10 Plenary Meeting #89 - January 15, 2009 Weber
& Lohmeyer HTM (141593) 2009/01/23

09-032r0 Minutes of T10 Plenary Meeting #89 - January 15, 2009 Weber
& Lohmeyer PDF (344891) 2009/01/23

Greg
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[Matthew Wilcox]

Post by Greg Freemyer
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.

Post by Greg Freemyer
08-356r4 SBC-3: WRITE SAME unmap bit David L. Black PDF (56608) 2008/12/10

Probably interesting. Haven't read it myself.

Post by Greg Freemyer
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.

Post by Greg Freemyer
08-149r7 SBC - Thin Provisioning Frederick Knight PDF (281001) 2008/12/08

That's the one I'm working from.

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

A newer version ... thought so.

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

Clearly related.

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

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

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

Probably tedious.

Post by Greg Freemyer
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.

[Ric Wheeler]

Post by Matthew Wilcox

Post by Greg Freemyer
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.

Post by Greg Freemyer
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.

Post by Matthew Wilcox

Post by Greg Freemyer
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.

Post by Matthew Wilcox

Post by Greg Freemyer
08-149r7 SBC - Thin Provisioning Frederick Knight PDF (281001) 2008/12/08

That's the one I'm working from.

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

A newer version ... thought so.

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

Clearly related.

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

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

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

Probably tedious.

Post by Greg Freemyer
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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