From: Andi Kleen <andi@firstfloor.org>
To: Peter Cordes <peter@cordes.ca>
Cc: Andi Kleen <andi@firstfloor.org>, xfs@oss.sgi.com
Subject: Re: RAID5/6 writes
Date: Wed, 1 Oct 2008 22:44:50 +0200 [thread overview]
Message-ID: <20081001204450.GA25711@one.firstfloor.org> (raw)
In-Reply-To: <20081001201331.GL32037@cordes.ca>
On Wed, Oct 01, 2008 at 05:13:31PM -0300, Peter Cordes wrote:
> On Wed, Oct 01, 2008 at 09:36:13PM +0200, Andi Kleen wrote:
> > Peter Cordes <peter@cordes.ca> writes:
> > >
> > > XFS knows (or should have been told by the admin with mkfs!) what the
> > > stripe geometry is: block size and stripe width. So it could apply
> > > this optimization only if it would make a write cover more whole
> > > blocks or whole stripes.
> >
> > It's a nice idea, but I don't think XFS knows the actual RAID level,
> > only the stripes. And for 0/1 it wouldn't be a good idea.
>
> Yeah, this would have to be a mount option, like stripewrite=1.
> There are already a few other essential mount options people need to
> learn about for big RAIDs, e.g. inode64.
The other problem I can think of is that determing if something is
free data might need more read IO if the free extent tree is not completely
cached.
-Andi
next prev parent reply other threads:[~2008-10-01 20:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-01 17:52 RAID5/6 writes Peter Cordes
2008-10-01 19:36 ` Andi Kleen
2008-10-01 20:13 ` Peter Cordes
2008-10-01 20:44 ` Andi Kleen [this message]
2008-10-01 21:01 ` Peter Cordes
2008-10-02 0:32 ` Dave Chinner
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