From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: David Buckley <dbuckley@oreilly.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
linux-scsi@vger.kernel.org
Subject: Re: problem with discard granularity in sd
Date: Tue, 11 Apr 2017 21:55:20 -0400 [thread overview]
Message-ID: <yq14lxuv187.fsf@oracle.com> (raw)
In-Reply-To: <CA+Xd3XG1AN-ZTjn3SfZffrY=4vezSS8RrE88jG0QEsuyHC5k8A@mail.gmail.com> (David Buckley's message of "Tue, 11 Apr 2017 11:07:43 -0700")
David,
> I am wondering if part of the issue is that in my use case, UNMAP and
> WRITE SAME zeros result in very different results. With thin
> provisioned LUNs, UNMAP requests result in the blocks being freed and
> thus reduces the actual size of the LUN allocation on disk. If WRITE
> SAME requests are used to zero the blocks, they remain allocated and
> thus the real size of the LUN grows to match the allocated size
> (effectively thick-provisioning the LUN).
The filer explicitly reported support for WRITE SAME(10/16) with UNMAP.
It seems very odd that it would then completely ignore the UNMAP bit and
do a regular WRITE SAME.
Are you running latest firmware, btw.?
In any case. The changes I mentioned are now queued up for 4.12. But
it'll obviously take a while for those to trickle into the
distributions...
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2017-04-12 1:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-11 18:07 problem with discard granularity in sd David Buckley
2017-04-12 1:55 ` Martin K. Petersen [this message]
2017-04-12 23:58 ` David Buckley
2017-04-14 2:44 ` Martin K. Petersen
2017-04-14 20:07 ` David Buckley
-- strict thread matches above, loose matches on Subject: below --
2017-03-31 16:52 David Buckley
2017-04-05 0:12 ` Martin K. Petersen
2017-04-05 16:14 ` David Buckley
2017-04-06 17:34 ` Martin K. Petersen
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