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Re: stable xfs

To: Chris Wedgwood <cw@xxxxxxxx>
Subject: Re: stable xfs
From: Ming Zhang <mingz@xxxxxxxxxxx>
Date: Wed, 19 Jul 2006 10:10:06 -0400
Cc: Peter Grandi <pg_xfs@xxxxxxxxxxxxxxxxxx>, Linux XFS <linux-xfs@xxxxxxxxxxx>
In-reply-to: <20060719055621.GA1491@xxxxxxxxxxxxxxxxxxxxx>
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Reply-to: mingz@xxxxxxxxxxx
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On Tue, 2006-07-18 at 22:56 -0700, Chris Wedgwood wrote:
> On Tue, Jul 18, 2006 at 09:20:44PM -0400, Ming Zhang wrote:
> 
> > when u say large parallel storage system, you mean independent
> > spindles right? but most people will have all disks configured in
> > one RAID5/6 and thus it is not parallel any more.
> 
> it depends, you might have 100s of spindles in groups, you don't make
> a giant raid5/6 array with that many disks, you make a number of
> smaller arrays

right

> 
> > i think with write barrier support, system without UPS should be ok.
> 
> with barrier support a UPS shouldn't be necessary
> 
> > considering even u have UPS, kernel oops in other parts still can
> > take the FS down.
> 

i mean with UPS and huge write cache, but no write barrier.

> but a crash won't cause writes to be 'reordered'
> 
> 
> reordering is bad because the fs pushes writes down in a manner that
> means when it comes back it will be able to make it self consistent,
> so if you have a number of writes pending and some of them are lost,
> and those that are lost are not the most recent writes because of
> reordering, you can end up with a corrupt fs


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