From: Ric Wheeler <rwheeler@redhat.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: dgilbert@interlog.com, hch@infradead.org, axboe@kernel.dk,
matthew@wil.cx, linux-scsi@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 2/2] sd: WRITE SAME(16) / UNMAP support
Date: Fri, 30 Oct 2009 12:02:41 -0400 [thread overview]
Message-ID: <4AEB0E21.4060401@redhat.com> (raw)
In-Reply-To: <yq1pr85scs4.fsf@sermon.lab.mkp.net>
On 10/30/2009 12:53 AM, Martin K. Petersen wrote:
>>>>>> "Doug" == Douglas Gilbert<dgilbert@interlog.com> writes:
>>>>>>
> Doug> And if both are supported by the logical unit, the patch prefers
> Doug> UNMAP?
>
> Yes.
>
> SBC states that if the device reports MAXIMUM UNMAP LBA COUNT> 1 and
> MAXIMUM UNMAP DESCRIPTOR COUNT> 1 then the device supports UNMAP. And
> in that case that's what I'll issue. In all other cases I'll send out
> WRITE SAME(16). I believe that approach is what's currently considered
> best practice.
>
This sounds like the correct thing to do.
We should at the same time try to unify the file system mount options so
we roll out the testing in a careful way.
Specifically, I would suggest that we default to "not" issuing discards
by default and that we try to use the same mount option for any file
system that supports barrier discards. My worry is that we will fry
SSD's (like the reported issues with the Intel SSD's and Windows 7) or
have horrific performance on arrays that are not tuned for fine grained
discards :-)
Ric
parent reply other threads:[~2009-10-30 16:02 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <yq1pr85scs4.fsf@sermon.lab.mkp.net>]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4AEB0E21.4060401@redhat.com \
--to=rwheeler@redhat.com \
--cc=axboe@kernel.dk \
--cc=dgilbert@interlog.com \
--cc=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=matthew@wil.cx \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).