linux-ext4 - Re: changing stride and stripe

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Message-id: <EA1A7036-FD43-4996-9665-E04FD32A449F@sun.com>
Date:	Tue, 20 Oct 2009 15:08:51 -0600
From:	Andreas Dilger <adilger@....com>
To:	Doug Hunley <doug@...ley.homeip.net>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: changing stride and stripe_width post-fs-creation?

On 20-Oct-09, at 11:32, Doug Hunley wrote:
> Is it safe to use tune2fs to alter stride and stripe_width on an ext4
> fs once it has been created? Any caveats I should know about? Thanks

The stride is mostly used at fs creation time, but there is no problem
with changing it.  The stripe_width is used by the allocator to align
file allocations with the RAID layout.

One question for Eric is whether the new libdisk patches he made will  
set
the stripe_width to something ridiculous like 512 or 4096 bytes, or if  
it
just leaves that field unset in that case.  I suspect it would be bad  
for
mballoc to see the stripe_width be such a small value.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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