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From: Anthony Liguori <anthony@codemonkey.ws>
To: Dor Laor <dor.laor@qumranet.com>
Cc: qemu-devel@nongnu.org, Chris Wright <chrisw@redhat.com>,
	Mark McLoughlin <markmc@redhat.com>,
	kvm-devel <kvm@vger.kernel.org>,
	Laurent Vivier <Laurent.Vivier@bull.net>,
	Ryan Harper <ryanh@us.ibm.com>
Subject: Re: [Qemu-devel] [RFC] Disk integrity in QEMU
Date: Sun, 12 Oct 2008 13:02:57 -0500	[thread overview]
Message-ID: <48F23BD1.9020109@codemonkey.ws> (raw)
In-Reply-To: <48F20BBC.1040708@il.qumranet.com>

Dor Laor wrote:
> Avi Kivity wrote:
>
> Since there is ongoing effort (both by IT and developers) to keep the 
> base images as big as possible, it guarantees that
> this data is best suited for caching in the host while the private 
> leaf images will be uncached.

A proper CAS solution is really such a better approach.  qcow2 
deduplification is an interesting concept, but such a hack :-)

> This way we provide good performance and caching for the shared parent 
> images while also promising correctness.

You get correctness by using O_DSYNC.  cache=off should disable the use 
of the page cache everywhere.

Regards,

Anthony Liguori

> Actually this is what happens on mainline qemu with cache=off.
>
> Cheers,
> Dor
> -- 
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


WARNING: multiple messages have this Message-ID (diff)
From: Anthony Liguori <anthony@codemonkey.ws>
To: Dor Laor <dor.laor@qumranet.com>
Cc: Chris Wright <chrisw@redhat.com>,
	Mark McLoughlin <markmc@redhat.com>,
	kvm-devel <kvm@vger.kernel.org>,
	Laurent Vivier <Laurent.Vivier@bull.net>,
	qemu-devel@nongnu.org, Ryan Harper <ryanh@us.ibm.com>
Subject: Re: [Qemu-devel] [RFC] Disk integrity in QEMU
Date: Sun, 12 Oct 2008 13:02:57 -0500	[thread overview]
Message-ID: <48F23BD1.9020109@codemonkey.ws> (raw)
In-Reply-To: <48F20BBC.1040708@il.qumranet.com>

Dor Laor wrote:
> Avi Kivity wrote:
>
> Since there is ongoing effort (both by IT and developers) to keep the 
> base images as big as possible, it guarantees that
> this data is best suited for caching in the host while the private 
> leaf images will be uncached.

A proper CAS solution is really such a better approach.  qcow2 
deduplification is an interesting concept, but such a hack :-)

> This way we provide good performance and caching for the shared parent 
> images while also promising correctness.

You get correctness by using O_DSYNC.  cache=off should disable the use 
of the page cache everywhere.

Regards,

Anthony Liguori

> Actually this is what happens on mainline qemu with cache=off.
>
> Cheers,
> Dor
> -- 
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

  parent reply	other threads:[~2008-10-12 18:03 UTC|newest]

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-09 17:00 [Qemu-devel] [RFC] Disk integrity in QEMU Anthony Liguori
2008-10-10  7:54 ` Gerd Hoffmann
2008-10-10  8:12   ` Mark McLoughlin
2008-10-12 23:10     ` Jamie Lokier
2008-10-14 17:15       ` Avi Kivity
2008-10-10  9:32   ` Avi Kivity
2008-10-12 23:00     ` Jamie Lokier
2008-10-10  8:11 ` Aurelien Jarno
2008-10-10 12:26   ` Anthony Liguori
2008-10-10 12:53     ` Paul Brook
2008-10-10 13:55       ` Anthony Liguori
2008-10-10 14:05         ` Paul Brook
2008-10-10 14:19         ` Avi Kivity
2008-10-17 13:14           ` Jens Axboe
2008-10-19  9:13             ` Avi Kivity
2008-10-10 15:48     ` Aurelien Jarno
2008-10-10  9:16 ` Avi Kivity
2008-10-10  9:58   ` Daniel P. Berrange
2008-10-10 10:26     ` Avi Kivity
2008-10-10 12:59       ` Paul Brook
2008-10-10 13:20         ` Avi Kivity
2008-10-10 12:34   ` Anthony Liguori
2008-10-10 12:56     ` Avi Kivity
2008-10-11  9:07     ` andrzej zaborowski
2008-10-11 17:54   ` Mark Wagner
2008-10-11 20:35     ` Anthony Liguori
2008-10-12  0:43       ` Mark Wagner
2008-10-12  1:50         ` Chris Wright
2008-10-12  1:50           ` Chris Wright
2008-10-12 16:22           ` Jamie Lokier
2008-10-12 16:22             ` Jamie Lokier
2008-10-12 17:54         ` Anthony Liguori
2008-10-12 18:14           ` nuitari-qemu
2008-10-13  0:27           ` Mark Wagner
2008-10-13  1:21             ` Anthony Liguori
2008-10-13  2:09               ` Mark Wagner
2008-10-13  3:16                 ` Anthony Liguori
2008-10-13  6:42                 ` Aurelien Jarno
2008-10-13 14:38                 ` Steve Ofsthun
2008-10-12  0:44       ` Chris Wright
2008-10-12 10:21         ` Avi Kivity
2008-10-12 14:37           ` Dor Laor
2008-10-12 14:37             ` Dor Laor
2008-10-12 15:35             ` Jamie Lokier
2008-10-12 18:00               ` Anthony Liguori
2008-10-12 18:02             ` Anthony Liguori [this message]
2008-10-12 18:02               ` Anthony Liguori
2008-10-15 10:17               ` Andrea Arcangeli
2008-10-15 10:17                 ` Andrea Arcangeli
2008-10-12 17:59           ` Anthony Liguori
2008-10-12 18:34             ` Avi Kivity
2008-10-12 19:33               ` Izik Eidus
2008-10-12 19:33                 ` Izik Eidus
2008-10-14 17:08                 ` Avi Kivity
2008-10-14 17:08                   ` Avi Kivity
2008-10-12 19:59               ` Anthony Liguori
2008-10-12 20:43                 ` Avi Kivity
2008-10-12 21:11                   ` Anthony Liguori
2008-10-14 15:21                     ` Avi Kivity
2008-10-14 15:32                       ` Anthony Liguori
2008-10-14 15:43                         ` Avi Kivity
2008-10-14 19:25                       ` Laurent Vivier
2008-10-16  9:47                         ` Avi Kivity
2008-10-12 10:12       ` Avi Kivity
2008-10-17 13:20         ` Jens Axboe
2008-10-19  9:01           ` Avi Kivity
2008-10-19 18:10             ` Jens Axboe
2008-10-19 18:23               ` Avi Kivity
2008-10-19 19:17                 ` M. Warner Losh
2008-10-19 19:31                   ` Avi Kivity
2008-10-19 18:24               ` Avi Kivity
2008-10-19 18:36                 ` Jens Axboe
2008-10-19 19:11                   ` Avi Kivity
2008-10-19 19:30                     ` Jens Axboe
2008-10-19 20:16                       ` Avi Kivity
2008-10-20 14:14                       ` Avi Kivity
2008-10-10 10:03 ` Fabrice Bellard
2008-10-13 16:11 ` Laurent Vivier
2008-10-13 16:58   ` Anthony Liguori
2008-10-13 17:36     ` Jamie Lokier
2008-10-13 17:06 ` [Qemu-devel] " Ryan Harper
2008-10-13 18:43   ` Anthony Liguori
2008-10-14 16:42     ` Avi Kivity
2008-10-13 18:51   ` Laurent Vivier
2008-10-13 19:43     ` Ryan Harper
2008-10-13 20:21       ` Laurent Vivier
2008-10-13 21:05         ` Ryan Harper
2008-10-15 13:10           ` Laurent Vivier
2008-10-16 10:24             ` Laurent Vivier
2008-10-16 13:43               ` Anthony Liguori
2008-10-16 16:08                 ` Laurent Vivier
2008-10-17 12:48                 ` Avi Kivity
2008-10-17 13:17                   ` Laurent Vivier
2008-10-14 10:05       ` Kevin Wolf
2008-10-14 14:32         ` Ryan Harper
2008-10-14 16:37       ` Avi Kivity
2008-10-13 19:00   ` Mark Wagner
2008-10-13 19:15     ` Ryan Harper
2008-10-14 16:49       ` Avi Kivity
2008-10-13 17:58 ` [Qemu-devel] " Rik van Riel
2008-10-13 18:22   ` Jamie Lokier
2008-10-13 18:34     ` Rik van Riel
2008-10-14  1:56       ` Jamie Lokier
2008-10-14  2:28         ` nuitari-qemu
2008-10-28 17:34 ` Ian Jackson
2008-10-28 17:45   ` Anthony Liguori
2008-10-28 17:50     ` Ian Jackson
2008-10-28 18:19       ` Jamie Lokier

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