From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: "Cláudio Martins" <ctpm@ist.utl.pt>
Cc: James Bottomley <James.Bottomley@suse.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Tejun Heo <tj@kernel.org>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Daniel Taylor <Daniel.Taylor@wdc.com>,
Jeff Garzik <jeff@garzik.org>, Mark Lord <kernel@teksavvy.com>,
tytso@mit.edu, hirofumi@mail.parknet.co.jp,
Andrew Morton <akpm@linux-foundation.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
irtiger@gmail.com, Matthew Wilcox <matthew@wil.cx>,
aschnell@suse.de, knikanth@suse.de, jdelvare@suse.de
Subject: Re: ATA 4 KiB sector issues.
Date: Mon, 08 Mar 2010 16:07:14 -0500 [thread overview]
Message-ID: <yq1bpeya5fh.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <20100308200206.dac60db7.ctpm@ist.utl.pt> ("Cláudio Martins"'s message of "Mon, 8 Mar 2010 20:02:06 +0000")
>>>>> "Cláudio" == Cláudio Martins <ctpm@ist.utl.pt> writes:
Cláudio> So the question is: what are hard drive makers guaranteeing (if
Cláudio> anything at all)?
No guarantees. Nothing that you can get in writing, anyway.
Cláudio> Was a 512B sector write really atomic?
Sometimes.
Cláudio> Is a 4k one?
Sometimes, maybe.
The problem with 4KB physical blocks is that if you do a partial or
misaligned write you'll end up having to do read-modify-write. And that
introduces are scenario where a subsequent write error will affect
logical blocks that were not part of the I/O request.
However, you also have that with regular drives because they often write
more than the actual block undergoing I/O. For instance to reduce
hotspot bleed to adjacent sectors.
There have been several unsuccessful attempts at nudging the drive
vendors into giving us real guarantees (supercapacitors, NVRAM or
flash-backed write cache). No luck so far. So people that care use
arrays with non-volatile caches.
--
Martin K. Petersen Oracle Linux Engineering
WARNING: multiple messages have this Message-ID (diff)
From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: "Cláudio Martins" <ctpm@ist.utl.pt>
Cc: James Bottomley <James.Bottomley@suse.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Tejun Heo <tj@kernel.org>,
"linux-ide\@vger.kernel.org" <linux-ide@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Daniel Taylor <Daniel.Taylor@wdc.com>,
Jeff Garzik <jeff@garzik.org>, Mark Lord <kernel@teksavvy.com>,
tytso@mit.edu, hirofumi@mail.parknet.co.jp,
Andrew Morton <akpm@linux-foundation.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
irtiger@gmail.com, Matthew Wilcox <matthew@wil.cx>,
aschnell@suse.de, knikanth@suse.de, jdelvare@suse.de
Subject: Re: ATA 4 KiB sector issues.
Date: Mon, 08 Mar 2010 16:07:14 -0500 [thread overview]
Message-ID: <yq1bpeya5fh.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <20100308200206.dac60db7.ctpm@ist.utl.pt> ("Cláudio Martins"'s message of "Mon, 8 Mar 2010 20:02:06 +0000")
>>>>> "Cláudio" == Cláudio Martins <ctpm@ist.utl.pt> writes:
Cláudio> So the question is: what are hard drive makers guaranteeing (if
Cláudio> anything at all)?
No guarantees. Nothing that you can get in writing, anyway.
Cláudio> Was a 512B sector write really atomic?
Sometimes.
Cláudio> Is a 4k one?
Sometimes, maybe.
The problem with 4KB physical blocks is that if you do a partial or
misaligned write you'll end up having to do read-modify-write. And that
introduces are scenario where a subsequent write error will affect
logical blocks that were not part of the I/O request.
However, you also have that with regular drives because they often write
more than the actual block undergoing I/O. For instance to reduce
hotspot bleed to adjacent sectors.
There have been several unsuccessful attempts at nudging the drive
vendors into giving us real guarantees (supercapacitors, NVRAM or
flash-backed write cache). No luck so far. So people that care use
arrays with non-volatile caches.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2010-03-08 21:09 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-08 3:48 ATA 4 KiB sector issues Tejun Heo
2010-03-08 3:48 ` Tejun Heo
2010-03-08 5:38 ` Greg Freemyer
2010-03-08 7:00 ` James Bottomley
2010-03-08 7:53 ` H. Peter Anvin
2010-03-08 15:34 ` Martin K. Petersen
2010-03-08 15:34 ` Martin K. Petersen
2010-03-09 22:36 ` Daniel Taylor
2010-03-09 22:36 ` Daniel Taylor
2010-03-09 22:46 ` Greg Freemyer
2010-03-10 0:05 ` Tejun Heo
2010-03-10 0:14 ` Daniel Taylor
2010-03-10 0:14 ` Daniel Taylor
2010-03-10 0:26 ` Tejun Heo
2010-03-10 0:36 ` H. Peter Anvin
2010-03-10 5:17 ` H. Peter Anvin
2010-03-10 7:09 ` Gabor Gombas
2010-03-10 0:32 ` H. Peter Anvin
2010-03-10 10:46 ` Johannes Stezenbach
2010-03-10 11:22 ` H. Peter Anvin
2010-03-08 7:56 ` H. Peter Anvin
2010-03-08 15:33 ` Martin K. Petersen
2010-03-08 15:33 ` Martin K. Petersen
2010-03-08 15:38 ` Martin K. Petersen
2010-03-08 15:38 ` Martin K. Petersen
2010-03-08 15:41 ` Martin K. Petersen
2010-03-08 15:41 ` Martin K. Petersen
2010-03-08 18:50 ` H. Peter Anvin
2010-03-08 18:58 ` James Bottomley
2010-03-08 19:11 ` H. Peter Anvin
2010-03-08 20:02 ` Cláudio Martins
2010-03-08 21:07 ` Martin K. Petersen [this message]
2010-03-08 21:07 ` Martin K. Petersen
2010-03-08 20:19 ` Martin K. Petersen
2010-03-08 20:19 ` Martin K. Petersen
2010-03-08 21:16 ` H. Peter Anvin
2010-03-10 0:34 ` Tejun Heo
2010-03-10 7:53 ` Matthew Wilcox
2010-03-10 13:47 ` Jeff Garzik
2010-03-10 16:19 ` Damian Lukowski
2010-03-11 13:04 ` Theodore Tso
2010-03-11 13:57 ` Nikanth Karthikesan
2010-03-11 14:28 ` Theodore Tso
2010-03-11 14:39 ` James Bottomley
2010-03-11 15:05 ` Nikanth Karthikesan
2010-03-11 15:25 ` tytso
2010-03-11 16:26 ` Gene Heskett
2010-03-11 16:26 ` Gene Heskett
2010-03-11 16:34 ` Greg Freemyer
2010-03-11 16:34 ` Greg Freemyer
2010-03-12 1:09 ` Tejun Heo
2010-03-11 14:48 ` Mike Snitzer
2010-03-11 15:00 ` Nikanth Karthikesan
2010-03-11 15:10 ` Tejun Heo
2010-03-11 16:01 ` Mike Snitzer
2010-03-11 18:26 ` Christoph Hellwig
2010-03-11 16:33 ` H. Peter Anvin
2010-03-08 15:18 ` Martin K. Petersen
2010-03-08 15:18 ` Martin K. Petersen
2010-03-08 18:29 ` H. Peter Anvin
2010-03-08 20:01 ` Martin K. Petersen
2010-03-08 20:01 ` Martin K. Petersen
2010-03-08 19:34 ` Mike Snitzer
2010-03-09 2:53 ` Tejun Heo
2010-03-09 3:20 ` Martin K. Petersen
2010-03-09 3:20 ` Martin K. Petersen
2010-03-09 6:53 ` Michael Tokarev
2010-03-09 10:01 ` Karel Zak
2010-03-09 10:16 ` Michael Tokarev
2010-03-09 11:15 ` Dave Chinner
2010-03-09 11:38 ` Michael Tokarev
2010-03-09 12:20 ` Dave Chinner
2010-03-09 11:50 ` Karel Zak
2010-03-09 12:18 ` Karel Zak
2010-03-10 5:06 ` Martin K. Petersen
2010-03-10 20:50 ` Henrique de Moraes Holschuh
2010-03-10 4:57 ` Martin K. Petersen
2010-03-10 4:57 ` Martin K. Petersen
2010-03-08 19:58 ` Karel Zak
2010-03-09 2:34 ` Tejun Heo
2010-03-09 2:42 ` Jeff Garzik
2010-03-09 2:49 ` Tejun Heo
2010-03-09 2:42 ` Tejun Heo
2010-03-09 3:11 ` Martin K. Petersen
2010-03-09 3:11 ` Martin K. Petersen
2010-03-09 3:09 ` Martin K. Petersen
2010-03-09 3:09 ` Martin K. Petersen
2010-03-09 3:38 ` Daniel Taylor
2010-03-09 3:38 ` Daniel Taylor
2010-03-09 4:54 ` Martin K. Petersen
2010-03-09 4:54 ` Martin K. Petersen
2010-03-09 3:41 ` Felix Miata
2010-03-09 7:27 ` Jim Meyering
2010-03-09 7:27 ` Jim Meyering
2010-03-09 23:56 ` Tejun Heo
2010-03-08 20:12 ` H. Peter Anvin
2010-03-09 2:22 ` Tejun Heo
2010-03-09 2:44 ` Tejun Heo
2010-03-09 3:18 ` Martin K. Petersen
2010-03-09 3:18 ` Martin K. Petersen
2010-03-09 14:32 ` Mark Lord
2010-03-09 6:34 ` Mikael Abrahamsson
2010-03-09 10:06 ` Michal Soltys
2010-03-10 0:11 ` Tejun Heo
2010-03-14 21:09 ` Michal Soltys
2010-03-14 22:56 ` s ponnusa
2010-03-09 13:55 ` Mark Lord
2010-03-10 0:00 ` Tejun Heo
2010-03-10 6:08 ` Mark Lord
2010-03-09 23:46 ` Arnd Bergmann
2010-03-10 0:20 ` Tejun Heo
2010-03-10 9:14 ` Denys Vlasenko
2010-03-10 11:02 ` Felix Miata
2010-03-15 1:21 ` H. Peter Anvin
2010-03-15 2:26 ` Denys Vlasenko
2010-03-15 2:56 ` Greg Freemyer
2010-03-15 4:00 ` H. Peter Anvin
2010-03-15 12:30 ` Arnd Bergmann
2010-03-15 5:20 ` david
2010-03-15 9:56 ` Denys Vlasenko
2010-03-15 14:47 ` H. Peter Anvin
2010-03-16 2:30 ` Tejun Heo
2010-03-16 2:32 ` Tejun Heo
2010-03-16 6:14 ` James Bottomley
2010-03-16 6:22 ` Tejun Heo
2010-03-16 6:37 ` Felix Miata
2010-03-16 6:42 ` Tejun Heo
2010-03-16 13:24 ` James Bottomley
2010-03-16 13:56 ` Tejun Heo
2010-03-16 14:21 ` James Bottomley
2010-03-16 14:25 ` Arnd Bergmann
2010-03-16 14:50 ` Tejun Heo
2010-03-16 15:02 ` James Bottomley
2010-03-16 15:20 ` Tejun Heo
2010-03-16 15:22 ` Martin K. Petersen
2010-03-16 15:22 ` Martin K. Petersen
2010-03-17 2:07 ` Tejun Heo
2010-03-16 15:23 ` James Bottomley
2010-03-16 15:37 ` Tejun Heo
2010-03-16 20:42 ` Ric Wheeler
2010-03-17 2:04 ` Tejun Heo
2010-03-17 2:51 ` Kevin Easton
2010-03-17 3:44 ` Tejun Heo
2010-03-17 8:01 ` jdow
2010-03-17 17:04 ` Bill Davidsen
2010-03-16 14:38 ` Denys Vlasenko
2010-03-16 15:12 ` Tejun Heo
2010-03-16 15:25 ` Denys Vlasenko
2010-03-16 15:47 ` Tejun Heo
2010-03-17 6:48 ` H. Peter Anvin
2010-03-16 6:27 ` Thomas Chou
-- strict thread matches above, loose matches on Subject: below --
2010-03-12 3:10 H. Peter Anvin
2010-03-16 22:21 H. Peter Anvin
2010-03-17 15:08 ` Ric Wheeler
2010-03-17 17:13 ` H. Peter Anvin
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