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From: Michael Tokarev <mjt@tls.msk.ru>
To: xfs@oss.sgi.com
Subject: Alignment size?
Date: Fri, 13 Aug 2010 02:10:39 +0400	[thread overview]
Message-ID: <4C64715F.8060000@msgid.tls.msk.ru> (raw)

Hello.

I used XFS for a long time on many different
servers, and it works well.  But now I encountered
an.. unexpected problem.

The question is: on one of our servers, XFS requires
different alignment size for O_DIRECT operations than
on others.  Usually it's 512 bytes, but on this server
it is 4096 - both min_io and alignment (this is from
XFS_IOC_DIOINFO ioctl).

I'm not sure what the reason for this is.
On this server, the underlying block device is raid5
(linux sw raid), but we had other machines with raid5
which didn't have that alignment requiriments.

The problem with that is that Oracle db, which we use
with XFS alot, refuses to work on this machine, or,
rather, XFS refuses to process I/O in 512-byte chunks
from oracle (control files and redolog files).

I know it is a frequent combination which is used in
production in many places, and is used here alot too,
but I haven't seen anyone mentioning this issue we
have now, with "larger than usual" alignment size
requiriments.

Is there a way to remedy this somehow, without
reformatting whole 600+ gb?

Thank you!

/mjt

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             reply	other threads:[~2010-08-12 22:10 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-12 22:10 Michael Tokarev [this message]
2010-08-12 23:49 ` Alignment size? Dave Chinner
2010-08-13  6:24   ` Michael Tokarev
2010-08-13 10:27     ` Stan Hoeppner
2010-08-13 11:00       ` Michael Tokarev
2010-08-13 11:36     ` Roger Willcocks
2010-08-13 11:39     ` Dave Chinner
2010-08-13 15:15       ` Christoph Hellwig
2010-08-17  0:18       ` Michael Tokarev
2010-08-17  0:30         ` Michael Tokarev
2010-08-17  0:31         ` Dave Chinner

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