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From: Eric Sandeen <sandeen@sandeen.net>
To: Michael Monnerie <michael.monnerie@is.it-management.at>
Cc: xfs@oss.sgi.com
Subject: Re: 4K drives, sectsz=512, bsize=4096
Date: Tue, 31 Aug 2010 17:15:29 -0500	[thread overview]
Message-ID: <4C7D7F01.1070003@sandeen.net> (raw)
In-Reply-To: <201009010007.23899@zmi.at>

Michael Monnerie wrote:
> On Dienstag, 31. August 2010 Eric Sandeen wrote:
>> Just be sure your first sector of your top-level block device
>> is 4k aligned, and then yes you'll want to set sector size to 4k
>> so that xfs will do all log IO in 4k blocks as well.
> 
> I can only hope LVM does it right, I have no idea how it aligns.
>  
>> If you do it right (and especially vs. if you do it wrong) it should
>> be a bit faster if all IOs are 4k aligned on the disk.
>  
> And that's what's interesting me: why? Won't XFS do all I/Os at minimum 
> for a given block size? Or is it possible XFS does write only a single 
> sector? I'd expect the smallest I/O size to be the block size, but it 
> seems I'm wrong?

the log can do things on sector size boundaries.
 
> I guess there's no way to "convert" an existing XFS with 
> sectsz=512,bsize=4096 to sectsz=4096,bsize=4096? Maybe that's only a 
> flag that can be changed?

I don't think so ...

-Eric

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  reply	other threads:[~2010-08-31 22:14 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-30  7:56 4K drives, sectsz=512, bsize=4096 Michael Monnerie
2010-08-31 21:01 ` Michael Monnerie
2010-08-31 21:16   ` Eric Sandeen
2010-08-31 22:07     ` Michael Monnerie
2010-08-31 22:15       ` Eric Sandeen [this message]
2010-08-31 23:12         ` Michael Monnerie
2010-08-31 22:34       ` Nathan Scott
2010-09-01  5:35         ` Gim Leong Chin
2010-09-01  5:59           ` Nathan Scott
2010-09-01  7:38           ` Michael Monnerie
2010-09-01 10:13             ` Christoph Hellwig
2010-09-01 10:24 ` Christoph Hellwig

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