From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Eric Sandeen <sandeen@sandeen.net>,
Carlos Maiolino <cmaiolino@redhat.com>,
xfs@oss.sgi.com
Subject: Re: [PATCH] libxfs: Get Physical Sector Size instead of Logical Sector size
Date: Mon, 28 Nov 2011 11:08:29 -0500 [thread overview]
Message-ID: <yq1vcq4grgi.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <20111127235051.GX2386@dastard> (Dave Chinner's message of "Mon, 28 Nov 2011 10:50:51 +1100")
>>>>> "Dave" == Dave Chinner <david@fromorbit.com> writes:
>> Ok, if we have mismanaged the alignment and aligned to logical, not
>> physical, then I guess there would be an issue... but at that point
>> we've already messed up (though not catastrophically I guess)...
Dave> That's where I'm concerned - if alignment is screwed because the
Dave> FS is 512B sector aligned (because something read the logical
Dave> sector size), then using a 4k sector will result in torn writes
Dave> because every 4k sector write is potentially made up of 2 4k write
Dave> IOs, not 1.
There's another inherent failure scenario with 512b logical / 4096b
physical. If you write in 512-byte multiples and experience a medium
error you can lose the sibling logical blocks within that physical
block. You'll get an I/O error back but there are no means to
communicate that you have also lost blocks that were not part of your
write request. So if you use 512-byte entries in the journal and get a
write error you should at the very minimum consider adjacent entries
inside a 4KB window suspect.
Dave> That's my concern - using the logical 512b sector size is -always-
Dave> safe, but using the 4k physical block size is only safe if
Dave> everything under the filesystem has detected and used the physical
Dave> block size of the disk for alignment and sector sizes...
You should always take alignment into account.
And while Christoph is right that (thankfully) nobody ended up shipping
drives with 1-alignment by default, most 512e drives have the alignment
jumper and some people actually use it.
--
Martin K. Petersen Oracle Linux Engineering
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2011-11-28 16:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-24 19:20 [PATCH] libxfs: Get Physical Sector Size instead of Logical Sector size Carlos Maiolino
2011-11-24 19:50 ` Carlos Maiolino
2011-11-27 1:06 ` Dave Chinner
2011-11-27 23:05 ` Eric Sandeen
2011-11-27 23:50 ` Dave Chinner
2011-11-28 7:56 ` Christoph Hellwig
2011-11-28 16:08 ` Martin K. Petersen [this message]
2011-11-28 16:11 ` Eric Sandeen
2011-11-29 17:15 ` Martin K. Petersen
2011-11-29 17:38 ` Eric Sandeen
2011-11-30 0:19 ` Dave Chinner
2011-11-30 15:03 ` Carlos Maiolino
2011-11-28 16:56 ` Greg Freemyer
2011-11-28 7:54 ` Christoph Hellwig
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=yq1vcq4grgi.fsf@sermon.lab.mkp.net \
--to=martin.petersen@oracle.com \
--cc=cmaiolino@redhat.com \
--cc=david@fromorbit.com \
--cc=sandeen@sandeen.net \
--cc=xfs@oss.sgi.com \
/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