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From: Christoph Hellwig <hch@lst.de>
To: Javier Guerra <javier@guerrag.com>
Cc: Christoph Hellwig <hch@lst.de>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org,
	rusty@rustcorp.com.au
Subject: Re: Notes on block I/O data integrity
Date: Tue, 25 Aug 2009 21:36:21 +0200	[thread overview]
Message-ID: <20090825193621.GA19778@lst.de> (raw)
In-Reply-To: <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com>

On Tue, Aug 25, 2009 at 02:33:30PM -0500, Javier Guerra wrote:
> On Tue, Aug 25, 2009 at 1:11 PM, Christoph Hellwig<hch@lst.de> wrote:
> > ??- barrier requests and cache flushes are supported by all local
> > ?? disk filesystem in popular use (btrfs, ext3, ext4, reiserfs, XFS).
> > ?? However unlike the other filesystems ext3 does _NOT_ enable barriers
> > ?? and cache flush requests by default.
> 
> what about LVM? iv'e read somewhere that it used to just eat barriers
> used by XFS, making it less safe than simple partitions.

Oh, any additional layers open another by cans of worms.  On Linux until
very recently using LVM or software raid means only disabled
write caches are safe.


WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Javier Guerra <javier@guerrag.com>
Cc: rusty@rustcorp.com.au, Christoph Hellwig <hch@lst.de>,
	kvm@vger.kernel.org, qemu-devel@nongnu.org
Subject: [Qemu-devel] Re: Notes on block I/O data integrity
Date: Tue, 25 Aug 2009 21:36:21 +0200	[thread overview]
Message-ID: <20090825193621.GA19778@lst.de> (raw)
In-Reply-To: <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com>

On Tue, Aug 25, 2009 at 02:33:30PM -0500, Javier Guerra wrote:
> On Tue, Aug 25, 2009 at 1:11 PM, Christoph Hellwig<hch@lst.de> wrote:
> > ??- barrier requests and cache flushes are supported by all local
> > ?? disk filesystem in popular use (btrfs, ext3, ext4, reiserfs, XFS).
> > ?? However unlike the other filesystems ext3 does _NOT_ enable barriers
> > ?? and cache flush requests by default.
> 
> what about LVM? iv'e read somewhere that it used to just eat barriers
> used by XFS, making it less safe than simple partitions.

Oh, any additional layers open another by cans of worms.  On Linux until
very recently using LVM or software raid means only disabled
write caches are safe.

  reply	other threads:[~2009-08-25 19:36 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-08-25 18:11 Notes on block I/O data integrity Christoph Hellwig
2009-08-25 18:11 ` [Qemu-devel] " Christoph Hellwig
2009-08-25 19:33 ` Javier Guerra
2009-08-25 19:33   ` [Qemu-devel] " Javier Guerra
2009-08-25 19:36   ` Christoph Hellwig [this message]
2009-08-25 19:36     ` Christoph Hellwig
2009-08-26 18:57     ` Jamie Lokier
2009-08-26 18:57       ` Jamie Lokier
2009-08-26 22:17       ` Christoph Hellwig
2009-08-26 22:17         ` Christoph Hellwig
2009-08-27  9:00         ` Jamie Lokier
2009-08-25 20:25 ` Nikola Ciprich
2009-08-25 20:25   ` [Qemu-devel] " Nikola Ciprich
2009-08-26 18:55   ` Jamie Lokier
2009-08-26 18:55     ` Jamie Lokier
2009-08-27  0:15   ` Christoph Hellwig
2009-08-27  0:15     ` [Qemu-devel] " Christoph Hellwig
2009-08-27 10:51 ` Rusty Russell
2009-08-27 10:51   ` [Qemu-devel] " Rusty Russell
2009-08-27 13:42   ` Christoph Hellwig
2009-08-27 13:42     ` [Qemu-devel] " Christoph Hellwig
2009-08-28  2:03     ` Rusty Russell
2009-08-28  2:03       ` [Qemu-devel] " Rusty Russell
2009-08-27 14:09 ` [Qemu-devel] " Jamie Lokier
2009-08-27 14:09   ` Jamie Lokier

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