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From: Ric Wheeler <rwheeler@redhat.com>
To: Mark Lord <lkml@rtr.ca>
Cc: Krzysztof Halasa <khc@pm.waw.pl>,
	Christoph Hellwig <hch@infradead.org>,
	Michael Tokarev <mjt@tls.msk.ru>,
	david@lang.hm, Pavel Machek <pavel@ucw.cz>,
	Theodore Tso <tytso@mit.edu>, NeilBrown <neilb@suse.de>,
	Rob Landley <rob@landley.net>, Florian Weimer <fweimer@bfk.de>,
	Goswin von Brederlow <goswin-v-b@web.de>,
	kernel list <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>,
	mtk.manpages@gmail.com, rdunlap@xenotime.net,
	linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org,
	corbet@lwn.net
Subject: Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage
Date: Sat, 05 Sep 2009 09:40:29 -0400	[thread overview]
Message-ID: <4AA26A4D.5090309@redhat.com> (raw)
In-Reply-To: <4AA26055.2090400@rtr.ca>

On 09/05/2009 08:57 AM, Mark Lord wrote:
> Ric Wheeler wrote:
>> On 09/04/2009 05:21 PM, Mark Lord wrote:
> ..
>>> How about instead, *fixing* the MD layer to properly support barriers?
>>> That would be far more useful, productive, and better for end-users.
> ..
>> Fixing MD would be great - not sure that it would end up still faster 
>> (look at md1 devices with working barriers with compared to md1 with 
>> write cache disabled).
> ..
>
> There's no inherent reason for it to be slower, except possibly
> drives with b0rked FUA support.
>
> So the first step is to fix MD to pass barriers to the LLDs
> for most/all RAID types.
> Then, if it has performance issues, those can be addressed
> by more application of little grey cells.  :)
>
> Cheers

The performance issue with MD is that the "simple" answer is to not only 
pass on those downstream barrier ops, but also to block and wait until 
all of those dependent barrier ops complete before ack'ing the IO.

When you do that implementation at least, you will see a very large 
performance impact and I am not sure that you would see any degradation 
vs just turning off the write caches.

Sounds like we should actually do some testing and actually measure, I 
do think that it will vary with the class of device quite a lot just 
like we see with single disk barriers vs write cache disabled on SAS vs 
S-ATA, etc...

ric


  reply	other threads:[~2009-09-05 13:41 UTC|newest]

Thread overview: 309+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-03-12  9:21 ext2/3: document conditions when reliable operation is possible Pavel Machek
2009-03-12 11:40 ` Jochen Voß
2009-03-21 11:24   ` Pavel Machek
2009-03-21 11:24     ` Pavel Machek
2009-03-12 19:13 ` Rob Landley
2009-03-16 12:28   ` Pavel Machek
2009-03-16 19:26     ` Rob Landley
2009-03-23 10:45       ` Pavel Machek
2009-03-30 15:06         ` Goswin von Brederlow
2009-08-24  9:26           ` Pavel Machek
2009-08-24  9:31           ` [patch] " Pavel Machek
2009-08-24 11:19             ` Florian Weimer
2009-08-24 13:01               ` Theodore Tso
2009-08-24 14:55                 ` Artem Bityutskiy
2009-08-24 22:30                   ` Rob Landley
2009-08-24 19:52                 ` Pavel Machek
2009-08-24 19:52                   ` Pavel Machek
2009-08-24 20:24                   ` Ric Wheeler
2009-08-24 20:52                     ` Pavel Machek
2009-08-24 21:08                       ` Ric Wheeler
2009-08-24 21:25                         ` Pavel Machek
2009-08-24 22:05                           ` Ric Wheeler
2009-08-24 22:22                             ` Zan Lynx
2009-08-24 22:44                               ` Pavel Machek
2009-08-25  0:34                                 ` Ric Wheeler
2009-08-24 23:42                               ` david
2009-08-24 22:41                             ` Pavel Machek
2009-08-24 22:39                           ` Theodore Tso
2009-08-24 23:00                             ` Pavel Machek
2009-08-25  0:02                               ` david
2009-08-25  9:32                                 ` Pavel Machek
2009-08-25  0:06                               ` Ric Wheeler
2009-08-25  9:34                                 ` Pavel Machek
2009-08-25 15:34                                   ` david
2009-08-26  3:32                                   ` Rik van Riel
2009-08-26 11:17                                     ` Pavel Machek
2009-08-26 11:29                                       ` david
2009-08-26 13:10                                         ` Pavel Machek
2009-08-26 13:43                                           ` david
2009-08-26 18:02                                             ` Theodore Tso
2009-08-27  6:28                                               ` Eric Sandeen
2009-08-27  6:28                                                 ` Eric Sandeen
2009-11-09  8:53                                               ` periodic fsck was " Pavel Machek
2009-11-09  8:53                                               ` Pavel Machek
2009-11-09 14:05                                                 ` Theodore Tso
2009-11-09 15:58                                                   ` Andreas Dilger
2009-08-30  7:03                                             ` Pavel Machek
2009-08-26 12:28                                       ` Theodore Tso
2009-08-27  6:06                                         ` Rob Landley
2009-08-27  6:54                                           ` david
2009-08-27  7:34                                             ` Rob Landley
2009-08-28 14:37                                               ` david
2009-08-30  7:19                                             ` Pavel Machek
2009-08-30 12:48                                               ` david
2009-08-27  5:27                                     ` Rob Landley
2009-08-25  0:08                               ` Theodore Tso
2009-08-25  9:42                                 ` Pavel Machek
2009-08-25  9:42                                 ` Pavel Machek
2009-08-25 13:37                                   ` Ric Wheeler
2009-08-25 13:42                                     ` Alan Cox
2009-08-27  3:16                                       ` Rob Landley
2009-08-25 21:15                                     ` Pavel Machek
2009-08-25 22:42                                       ` Ric Wheeler
2009-08-25 22:51                                         ` Pavel Machek
2009-08-25 23:03                                           ` david
2009-08-25 23:29                                             ` Pavel Machek
2009-08-25 23:03                                           ` Ric Wheeler
2009-08-25 23:26                                             ` Pavel Machek
2009-08-25 23:40                                               ` Ric Wheeler
2009-08-25 23:48                                                 ` david
2009-08-25 23:53                                                 ` Pavel Machek
2009-08-26  0:11                                                   ` Ric Wheeler
2009-08-26  0:16                                                     ` Pavel Machek
2009-08-26  0:31                                                       ` Ric Wheeler
2009-08-26  1:00                                                         ` Theodore Tso
2009-08-26  1:15                                                           ` Ric Wheeler
2009-08-26  2:58                                                             ` Theodore Tso
2009-08-26 10:39                                                               ` Ric Wheeler
2009-08-26 10:39                                                               ` Ric Wheeler
2009-08-26 11:12                                                                 ` Pavel Machek
2009-08-26 11:28                                                                   ` david
2009-08-29  9:49                                                                     ` [testcase] test your fs/storage stack (was Re: [patch] ext2/3: document conditions when reliable operation is possible) Pavel Machek
2009-08-29 11:28                                                                       ` Ric Wheeler
2009-09-02 20:12                                                                         ` Pavel Machek
2009-09-02 20:42                                                                           ` Ric Wheeler
2009-09-02 23:00                                                                             ` Rob Landley
2009-09-02 23:09                                                                               ` david
2009-09-03  8:55                                                                                 ` Pavel Machek
2009-09-03  0:36                                                                               ` jim owens
2009-09-03  2:41                                                                                 ` Rob Landley
2009-09-03 14:14                                                                                   ` jim owens
2009-09-04  7:44                                                                                     ` Rob Landley
2009-09-04 11:49                                                                                       ` Ric Wheeler
2009-09-05 10:28                                                                                         ` Pavel Machek
2009-09-05 12:20                                                                                           ` Ric Wheeler
2009-09-05 13:54                                                                                           ` Jonathan Corbet
2009-09-05 21:27                                                                                             ` Pavel Machek
2009-09-05 21:56                                                                                               ` Theodore Tso
2009-09-02 22:45                                                                           ` Rob Landley
2009-09-02 22:49                                                                           ` [PATCH] Update Documentation/md.txt to mention journaling won't help dirty+degraded case Rob Landley
2009-09-03  9:08                                                                             ` Pavel Machek
2009-09-03 12:05                                                                             ` Ric Wheeler
2009-09-03 12:31                                                                               ` Pavel Machek
2009-08-29 16:35                                                                       ` [testcase] test your fs/storage stack (was Re: [patch] ext2/3: document conditions when reliable operation is possible) david
2009-08-29 16:35                                                                         ` david
2009-08-30  7:07                                                                         ` Pavel Machek
2009-08-26 12:01                                                                   ` [patch] ext2/3: document conditions when reliable operation is possible Ric Wheeler
2009-08-26 12:23                                                                   ` Theodore Tso
2009-08-30  7:01                                                                     ` Pavel Machek
2009-08-30  7:01                                                                     ` Pavel Machek
2009-08-27  5:19                                                               ` Rob Landley
2009-08-27 12:24                                                                 ` Theodore Tso
2009-08-27 13:10                                                                   ` Ric Wheeler
2009-08-27 13:10                                                                   ` Ric Wheeler
2009-08-27 16:54                                                                     ` MD/DM and barriers (was Re: [patch] ext2/3: document conditions when reliable operation is possible) Jeff Garzik
2009-08-27 18:09                                                                       ` Alasdair G Kergon
2009-09-01 14:01                                                                       ` Pavel Machek
2009-09-02 16:17                                                                         ` Michael Tokarev
2009-08-29 10:02                                                                   ` [patch] ext2/3: document conditions when reliable operation is possible Pavel Machek
2009-08-29 10:02                                                                   ` Pavel Machek
2009-08-26  1:15                                                           ` Ric Wheeler
2009-08-26  1:16                                                           ` Pavel Machek
2009-08-26  1:16                                                           ` Pavel Machek
2009-08-26  2:55                                                             ` Theodore Tso
2009-08-26 13:37                                                               ` Ric Wheeler
2009-08-26 13:37                                                               ` Ric Wheeler
2009-08-26  2:53                                                           ` Henrique de Moraes Holschuh
2009-08-26  2:53                                                           ` Henrique de Moraes Holschuh
2009-09-03  9:47                                                           ` Pavel Machek
2009-09-03  9:47                                                             ` Pavel Machek
2009-08-26  3:50                                                   ` Rik van Riel
2009-08-27  3:53                                                 ` Rob Landley
2009-08-27 11:43                                                   ` Ric Wheeler
2009-08-27 20:51                                                     ` Rob Landley
2009-08-27 22:00                                                       ` Ric Wheeler
2009-08-28 14:49                                                       ` david
2009-08-29 10:05                                                         ` Pavel Machek
2009-08-29 20:22                                                           ` Rob Landley
2009-08-29 21:34                                                             ` Pavel Machek
2009-09-03 16:56                                                             ` what fsck can (and can't) do was " david
2009-09-03 19:27                                                               ` Theodore Tso
2009-08-27 22:13                                                     ` raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) Pavel Machek
2009-08-28  1:32                                                       ` Ric Wheeler
2009-08-28  6:44                                                         ` Pavel Machek
2009-08-28  7:31                                                           ` NeilBrown
2009-08-28  7:31                                                             ` NeilBrown
2009-11-09 10:50                                                             ` Pavel Machek
2009-08-28 11:16                                                           ` Ric Wheeler
2009-09-01 13:58                                                             ` Pavel Machek
2009-08-28  7:11                                                         ` raid is dangerous but that's secret Florian Weimer
2009-08-28  7:23                                                           ` NeilBrown
2009-08-28 12:08                                                         ` raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) Theodore Tso
2009-08-30  7:51                                                           ` Pavel Machek
2009-08-30  9:01                                                             ` Christian Kujau
2009-09-02 20:55                                                               ` Pavel Machek
2009-08-30 12:55                                                             ` david
2009-08-30 14:12                                                               ` Ric Wheeler
2009-08-30 14:44                                                                 ` Michael Tokarev
2009-08-30 16:10                                                                   ` Ric Wheeler
2009-08-30 16:35                                                                   ` Christoph Hellwig
2009-08-31 13:15                                                                     ` Ric Wheeler
2009-08-31 13:16                                                                       ` Christoph Hellwig
2009-08-31 13:19                                                                         ` Mark Lord
2009-08-31 13:21                                                                           ` Christoph Hellwig
2009-08-31 15:14                                                                             ` jim owens
2009-09-03  1:59                                                                             ` Ric Wheeler
2009-09-03 11:12                                                                               ` Krzysztof Halasa
2009-09-03 11:18                                                                                 ` Ric Wheeler
2009-09-03 13:34                                                                                   ` Krzysztof Halasa
2009-09-03 13:50                                                                                     ` Ric Wheeler
2009-09-03 13:59                                                                                       ` Krzysztof Halasa
2009-09-03 14:15                                                                                         ` wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage Ric Wheeler
2009-09-03 14:26                                                                                           ` Florian Weimer
2009-09-03 15:09                                                                                             ` Ric Wheeler
2009-09-03 23:50                                                                                           ` Krzysztof Halasa
2009-09-04  0:39                                                                                             ` Ric Wheeler
2009-09-04 21:21                                                                                           ` Mark Lord
2009-09-04 21:29                                                                                             ` Ric Wheeler
2009-09-05 12:57                                                                                               ` Mark Lord
2009-09-05 13:40                                                                                                 ` Ric Wheeler [this message]
2009-09-05 21:43                                                                                                 ` NeilBrown
2009-09-07 11:45                                                                                           ` Pavel Machek
2009-09-07 13:10                                                                                             ` Theodore Tso
2010-04-04 13:47                                                                                               ` fsck more often when powerfail is detected (was Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage) Pavel Machek
2010-04-04 13:47                                                                                                 ` Pavel Machek
2010-04-04 17:39                                                                                                 ` tytso
2010-04-04 17:59                                                                                                 ` Rob Landley
2010-04-04 18:45                                                                                                   ` Pavel Machek
2010-04-04 19:35                                                                                                     ` tytso
2010-04-04 19:29                                                                                                   ` tytso
2010-04-04 23:58                                                                                                     ` Rob Landley
2009-09-03 14:35                                                                                     ` raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) david
2009-08-31 13:22                                                                         ` Ric Wheeler
2009-08-31 15:50                                                                           ` david
2009-08-31 16:21                                                                             ` Ric Wheeler
2009-08-31 18:31                                                                             ` Christoph Hellwig
2009-08-31 19:11                                                                               ` david
2009-08-30 15:05                                                               ` Pavel Machek
2009-08-30 15:20                                                             ` Theodore Tso
2009-08-31 17:49                                                               ` Jesse Brandeburg
2009-08-31 18:01                                                                 ` Ric Wheeler
2009-08-31 21:01                                                                   ` MD5/6? (was Re: raid is dangerous but that's secret ...) Ron Johnson
2009-08-31 18:07                                                                 ` raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) martin f krafft
2009-08-31 22:26                                                                   ` Jesse Brandeburg
2009-08-31 22:26                                                                     ` Jesse Brandeburg
2009-08-31 23:19                                                                     ` Ron Johnson
2009-09-01  5:45                                                                     ` martin f krafft
2009-08-31 17:49                                                               ` Jesse Brandeburg
2009-09-05 10:34                                                               ` Pavel Machek
2009-09-05 10:34                                                               ` Pavel Machek
2009-08-30  7:51                                                           ` Pavel Machek
2009-08-25 23:46                                               ` [patch] ext2/3: document conditions when reliable operation is possible david
2009-08-25 23:08                                       ` Neil Brown
2009-08-25 23:44                                         ` Pavel Machek
2009-08-26  4:08                                           ` Rik van Riel
2009-08-26 11:15                                             ` Pavel Machek
2009-08-27  3:29                                               ` Rik van Riel
2009-08-25 16:11                                   ` Theodore Tso
2009-08-25 22:21                                     ` [patch] document flash/RAID dangers Pavel Machek
2009-08-25 22:21                                       ` Pavel Machek
2009-08-25 22:33                                       ` david
2009-08-25 22:40                                         ` Pavel Machek
2009-08-25 22:59                                           ` david
2009-08-25 23:37                                             ` Pavel Machek
2009-08-25 23:48                                               ` Ric Wheeler
2009-08-26  0:06                                                 ` Pavel Machek
2009-08-26  0:12                                                   ` Ric Wheeler
2009-08-26  0:20                                                     ` Pavel Machek
2009-08-26  0:26                                                       ` david
2009-08-26  0:28                                                       ` Ric Wheeler
2009-08-26  0:38                                                         ` Pavel Machek
2009-08-26  0:45                                                           ` Ric Wheeler
2009-08-26 11:21                                                             ` Pavel Machek
2009-08-26 11:58                                                               ` Ric Wheeler
2009-08-26 12:40                                                                 ` Theodore Tso
2009-08-26 13:11                                                                   ` Ric Wheeler
2009-08-26 13:11                                                                   ` Ric Wheeler
2009-08-26 13:44                                                                     ` david
2009-08-26 13:40                                                                   ` Chris Adams
2009-08-26 13:47                                                                     ` Alan Cox
2009-08-26 14:11                                                                       ` Chris Adams
2009-08-27 21:50                                                                     ` Pavel Machek
2009-08-29  9:38                                                                 ` Pavel Machek
2009-08-26  4:24                                                       ` Rik van Riel
2009-08-26 11:22                                                         ` Pavel Machek
2009-08-26 14:45                                                           ` Rik van Riel
2009-08-29  9:39                                                             ` Pavel Machek
2009-08-29 11:47                                                               ` Ron Johnson
2009-08-29 16:12                                                                 ` jim owens
2009-08-25 23:56                                               ` david
2009-08-26  0:12                                                 ` Pavel Machek
2009-08-26  0:20                                                   ` david
2009-08-26  0:39                                                     ` Pavel Machek
2009-08-26  1:17                                                       ` david
2009-08-26  0:26                                                   ` Ric Wheeler
2009-08-26  0:44                                                     ` Pavel Machek
2009-08-26  0:50                                                       ` Ric Wheeler
2009-08-26  1:19                                                       ` david
2009-08-26 11:25                                                         ` Pavel Machek
2009-08-26 12:37                                                           ` Theodore Tso
2009-08-30  6:49                                                             ` Pavel Machek
2009-08-30  6:49                                                             ` Pavel Machek
2009-08-26  4:20                                           ` Rik van Riel
2009-08-25 22:27                                     ` [patch] document that ext2 can't handle barriers Pavel Machek
2009-08-25 22:27                                     ` Pavel Machek
2009-08-27  3:34                                 ` [patch] ext2/3: document conditions when reliable operation is possible Rob Landley
2009-08-27  8:46                                 ` David Woodhouse
2009-08-28 14:46                                   ` david
2009-08-29 10:09                                     ` Pavel Machek
2009-08-29 16:27                                       ` david
2009-08-29 21:33                                         ` Pavel Machek
2009-08-24 23:00                             ` Pavel Machek
2009-08-25 13:57                             ` Chris Adams
2009-08-25 22:58                             ` Neil Brown
2009-08-25 23:10                               ` Ric Wheeler
2009-08-25 23:32                                 ` NeilBrown
2009-08-25 23:32                                   ` NeilBrown
2009-08-24 21:11                       ` Greg Freemyer
2009-08-24 21:11                         ` Greg Freemyer
2009-08-25 20:56                         ` Rob Landley
2009-08-25 21:08                           ` david
2009-08-25 18:52                     ` Rob Landley
2009-08-25 14:43                 ` Florian Weimer
2009-08-24 13:50               ` Theodore Tso
2009-08-24 18:48                 ` Pavel Machek
2009-08-24 18:48                 ` Pavel Machek
2009-08-24 18:39               ` Pavel Machek
2009-08-24 13:21             ` Greg Freemyer
2009-08-24 13:21               ` Greg Freemyer
2009-08-24 18:44               ` Pavel Machek
2009-08-25 23:28               ` Neil Brown
2009-08-25 23:28                 ` Neil Brown
2009-08-26  1:34                 ` david
2009-08-24 21:11             ` Rob Landley
2009-08-24 21:33               ` Pavel Machek
2009-08-25 18:45                 ` Jan Kara
2009-03-16 12:30   ` Pavel Machek
2009-03-16 19:03     ` Theodore Tso
2009-03-23 18:23       ` Pavel Machek
2009-03-23 18:23         ` Pavel Machek
2009-03-16 19:40     ` Sitsofe Wheeler
2009-03-16 21:43       ` Rob Landley
2009-03-17  4:55         ` Kyle Moffett
2009-03-23 11:00       ` Pavel Machek
2009-08-29  1:33   ` Robert Hancock
2009-08-29 13:04     ` Alan Cox
2009-03-16 19:45 ` Greg Freemyer
2009-03-16 19:45   ` Greg Freemyer
2009-03-16 21:48   ` Pavel Machek
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     [not found] ` <dddWc-83W-51@gated-at.bofh.it>
     [not found]   ` <ddefx-5R-37@gated-at.bofh.it>
     [not found]     ` <ddep7-bI-7@gated-at.bofh.it>
     [not found]       ` <ddeyR-iy-11@gated-at.bofh.it>
     [not found]         ` <ddeyR-iy-9@gated-at.bofh.it>
     [not found]           ` <ddeIu-n9-9@gated-at.bofh.it>
     [not found]             ` <ddeSb-th-29@gated-at.bofh.it>
     [not found]               ` <ddoRI-11a-39@gated-at.bofh.it>
     [not found] <ciPTu-7f2-47@gated-at.bofh.it>
     [not found] ` <clrhX-3R1-13@gated-at.bofh.it>
     [not found]   ` <dcEc1-33Z-17@gated-at.bofh.it>
     [not found]     ` <dcFUz-4yN-9@gated-at.bofh.it>
     [not found]       ` <dcHtf-5XC-17@gated-at.bofh.it>
     [not found]         ` <dcNSc-2DU-11@gated-at.bofh.it>
     [not found]           ` <dcOl9-3aC-19@gated-at.bofh.it>
     [not found]             ` <dcOOd-3qM-33@gated-at.bofh.it>
     [not found]               ` <dcOXN-3M5-15@gated-at.bofh.it>

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