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From: Eric Sandeen <sandeen@sandeen.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Daniel Phillips <phillips@google.com>,
	Pavel Machek <pavel@ucw.cz>, David Chinner <dgc@sgi.com>,
	Theodore Tso <tytso@mit.edu>, Al Boldi <a1426z@gawab.com>,
	Valerie Henson <val.henson@gmail.com>,
	Rik van Riel <riel@redhat.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck)
Date: Wed, 16 Jan 2008 15:28:20 -0600	[thread overview]
Message-ID: <478E76F4.3090605@sandeen.net> (raw)
In-Reply-To: <20080116001503.3c0c97cf@lxorguk.ukuu.org.uk>

Alan Cox wrote:
>> Writeback cache on disk in iteself is not bad, it only gets bad if the
>> disk is not engineered to save all its dirty cache on power loss,
>> using the disk motor as a generator or alternatively a small battery.
>> It would be awfully nice to know which brands fail here, if any,
>> because writeback cache is a big performance booster.
> 
> AFAIK no drive saves the cache. The worst case cache flush for drives is
> several seconds with no retries and a couple of minutes if something
> really bad happens.
> 
> This is why the kernel has some knowledge of barriers and uses them to
> issue flushes when needed.

Problem is, ext3 has barriers off by default so it's not saving most people.

And then if you turn them on, but have your filesystem on an lvm device,
lvm strips them out again.

-Eric

  parent reply	other threads:[~2008-01-16 21:29 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-08 21:22 [RFD] Incremental fsck Al Boldi
2008-01-08 21:31 ` Alan
2008-01-09  9:16   ` Andreas Dilger
2008-01-12 23:55     ` Daniel Phillips
2008-01-08 21:41 ` Rik van Riel
2008-01-09  4:40   ` Al Boldi
2008-01-09  7:45     ` Valerie Henson
2008-01-09 11:52       ` Al Boldi
2008-01-09 14:44         ` Rik van Riel
2008-01-10 13:26           ` Al Boldi
2008-01-12 14:51         ` Theodore Tso
2008-01-13 11:05           ` Al Boldi
2008-01-13 17:19           ` Pavel Machek
2008-01-13 17:41             ` Alan Cox
2008-01-15 20:16               ` [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck) Pavel Machek
2008-01-15 21:43                 ` David Chinner
2008-01-15 23:07                   ` Pavel Machek
2008-01-15 23:44                     ` Daniel Phillips
2008-01-16  0:15                       ` Alan Cox
2008-01-16  1:24                         ` Daniel Phillips
2008-01-16  1:36                           ` Chris Mason
2008-01-17 20:54                             ` Pavel Machek
2008-01-16 19:06                           ` Bryan Henderson
2008-01-16 20:05                             ` Alan Cox
2008-01-17  2:02                             ` Daniel Phillips
2008-01-17 21:37                               ` Bryan Henderson
2008-01-17 22:45                               ` Theodore Tso
2008-01-17 22:58                                 ` Alan Cox
2008-01-17 23:18                                 ` Ric Wheeler
2008-01-18  0:31                                   ` Bryan Henderson
2008-01-18 14:23                                     ` Theodore Tso
2008-01-18 15:16                                       ` [Patch] document ext3 requirements (was Re: [RFD] Incrementalfsck) linux-os (Dick Johnson)
2008-01-19 14:53                                         ` Pavel Machek
2008-01-18 15:26                                       ` [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck) Ric Wheeler
2008-01-18 20:34                                         ` Jeff Garzik
2008-01-18 22:35                                           ` Bryan Henderson
2008-01-18 15:08                                     ` H. Peter Anvin
2008-01-18 17:43                                       ` Bryan Henderson
2008-01-16 21:28                         ` Eric Sandeen [this message]
2008-01-16 11:51                       ` Pavel Machek
2008-01-16 12:20                         ` Valdis.Kletnieks
2008-01-19 14:51                           ` Pavel Machek
2008-01-16 16:38                   ` Christoph Hellwig
2008-01-16  1:44                 ` Daniel Phillips
2008-01-16  3:05                   ` Rik van Riel
2008-01-17  7:38                     ` Andreas Dilger
2008-01-16 11:49                   ` Pavel Machek
2008-01-16 20:52                     ` Valerie Henson
2008-01-17 12:29                   ` Szabolcs Szakacsits
2008-01-17 22:51                     ` Daniel Phillips
2008-01-15  1:04             ` [RFD] Incremental fsck Ric Wheeler
2008-01-14  0:22           ` Daniel Phillips
2008-01-09  8:04     ` Valdis.Kletnieks

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