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From: Neil Brown <neilb@suse.de>
To: SandeepKsinha <sandeepksinha@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Change Chunk Size on Array?
Date: Wed, 13 May 2009 14:45:47 +1000	[thread overview]
Message-ID: <18954.20603.952706.467047@notabene.brown> (raw)
In-Reply-To: message from SandeepKsinha on Tuesday May 12

On Tuesday May 12, sandeepksinha@gmail.com wrote:
> 
> 
> 
> crshman wrote:
> > 
> > Hello All,
> > 
> > I wanted to know if it were possible to change the chunk size on an array
> > after it has been created. I have a software raid 5 comprised of 7 drives
> > with a chunk size of 64k. I wanted to up that to 1024k, would this be
> > possible without losing any data? This isn't mission critical so it is ok
> > if i need to stop the array first, however I'd rather not lose any data.
> > 
> It is possible to change the chunksize but for the same you would need to
> offline your array.

Is it?  How?

Online changing of chunk size for raid5 is very close to being
implemented.
All the kernel side support will be in 2.6.30.
I just need to spend some time getting mdadm to make it work.
Because data is being rearranged in-place, and because you don't want
to lose everything if your systems crashes, mdadm will have to work in
tandem with the kernel making a backup copy of a section of the array,
allowing the kernel to reshape that section, and then moving on to the
next section.  It will be slow, but it will be reliable.

NeilBrown

  reply	other threads:[~2009-05-13  4:45 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-19  5:29 Change Chunk Size on Array? crshman
2008-03-20  8:16 ` Justin Piszcz
2009-05-13  3:44 ` SandeepKsinha
2009-05-13  4:45   ` Neil Brown [this message]
2009-05-13  4:53     ` SandeepKsinha
2009-05-13  7:33     ` Goswin von Brederlow
2009-05-13 10:49       ` Neil Brown

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