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From: Marc MERLIN <marc@merlins.org>
To: Chris Mason <chris.mason@oracle.com>,
	linux-btrfs@vger.kernel.org, mbroz@redhat.com
Cc: jeff@deserettechnology.com
Subject: Re: brtfs on top of dmcrypt with SSD. No corruption iff write cache off?
Date: Sun, 12 Feb 2012 14:32:42 -0800	[thread overview]
Message-ID: <20120212223242.GA31989@merlins.org> (raw)
In-Reply-To: <20120202152722.GI12429@merlins.org> <20120202032345.GB31903@merlins.org>

On Thu, Feb 02, 2012 at 07:27:22AM -0800, Marc MERLIN wrote:
> On Thu, Feb 02, 2012 at 07:42:41AM -0500, Chris Mason wrote:
> > On Wed, Feb 01, 2012 at 07:23:45PM -0800, Marc MERLIN wrote:
> > > On Wed, Feb 01, 2012 at 12:56:24PM -0500, Chris Mason wrote:
> > > > > Second, I was wondering if anyone is running btrfs over dmcrypt on an SSD
> > > > > and what the performance is like with write cache turned off (I'm actually
> > > > > not too sure what the impact is for SSDs considering that writing to flash
> > > > > can actually be slower than writing to a hard drive).
> > > > 
> > > > Performance without the cache on is going to vary wildly from one SSD to
> > > > another.  Some really need it to give them nice fat writes while others
> > > > do better on smaller writes.  It's best to just test yours and see.
> > > > 
> > > > With a 3.2 kernel (it really must be 3.2 or higher), both btrfs and dm
> > > > are doing the right thing for barriers.
> > > 
> > > Thanks for the answer.
> > > Can you confirm that I still must disable write cache on the SSD to avoid
> > > corruption with btrfs on top of dmcrypt, or is there a chance that it just
> > > works now?
> > 
> > No, with 3.2 or higher it is expected to work.  dm-crypt is doing the
> > barriers correctly and as of 3.2 btrfs is sending them down correctly.
> 
> Thanks for confirming, I'll give this a shot.
> (no warranty implied of course :) ).

Actually I had one more question.

I read this page:
http://www.redhat.com/archives/dm-devel/2011-July/msg00042.html

I'm not super clear if with 3.2.5 kernel, I need to pass the special
allow_discards option for brtfs and dm-crypt to be safe together, or whether
they now talk through an API and everything "just works" :)

Thanks,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  

  parent reply	other threads:[~2012-02-12 22:32 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-30  0:37 brtfs on top of dmcrypt with SSD. No corruption iff write cache off? Marc MERLIN
2012-02-01 17:56 ` Chris Mason
2012-02-02  3:23   ` Marc MERLIN
2012-02-02 12:42     ` Chris Mason
     [not found]       ` <20120202152722.GI12429@merlins.org>
2012-02-12 22:32         ` Marc MERLIN [this message]
2012-02-12 23:47           ` Milan Broz
2012-02-13  0:14             ` Marc MERLIN
2012-02-15 15:42               ` Calvin Walton
2012-02-15 16:55                 ` Marc MERLIN
2012-02-15 16:59                   ` Hugo Mills
2012-02-22 10:28                     ` Justin Ossevoort
2012-02-22 11:07                       ` Hugo Mills
2012-02-16  6:33               ` Chris Samuel
2012-02-18 12:33               ` Martin Steigerwald
2012-02-18 12:39               ` Martin Steigerwald
2012-02-18 12:49                 ` Martin Steigerwald
2012-07-18 18:13               ` brtfs on top of dmcrypt with SSD -> Trim or no Trim Marc MERLIN
2012-07-18 20:04                 ` Fajar A. Nugraha
2012-07-18 20:37                   ` Marc MERLIN
2012-07-18 21:34                   ` Clemens Eisserer
2012-07-18 21:48                     ` Marc MERLIN
2012-07-18 21:49                 ` Martin Steigerwald
2012-07-18 22:04                   ` Marc MERLIN
2012-07-19 10:40                     ` Martin Steigerwald
2012-07-22 18:58                     ` brtfs on top of dmcrypt with SSD -> ssd or nossd + crypt performance? Marc MERLIN
2012-07-22 19:35                       ` Martin Steigerwald
2012-07-22 19:43                         ` Martin Steigerwald
2012-07-22 20:44                         ` Marc MERLIN
2012-07-22 22:41                           ` brtfs on top of dmcrypt with SSD -> file access 5x slower than spinning disk Marc MERLIN
2012-07-23  6:42                             ` How can btrfs take 23sec to stat 23K files from an SSD? Marc MERLIN
2012-07-24  7:56                               ` Martin Steigerwald
2012-07-27  4:40                                 ` Marc MERLIN
2012-07-27 11:08                               ` Chris Mason
2012-07-27 18:42                                 ` Marc MERLIN
2012-02-18 16:07             ` brtfs on top of dmcrypt with SSD. No corruption iff write cache off? Marc MERLIN
2012-02-19  0:53               ` Clemens Eisserer
2012-07-25 15:45 du -s src is a lot slower on SSD than spinning disk in the same laptop Marc MERLIN
     [not found] ` <alpine.LFD.2.00.1207252023080.4340@(none)>
2012-07-25 23:38   ` Marc MERLIN
2012-07-26  3:32   ` Ted Ts'o
2012-07-26  3:35     ` Marc MERLIN
2012-07-26  6:54     ` Marc MERLIN
2012-08-01  5:30       ` Marc MERLIN
2012-08-01  6:01         ` How can btrfs take 23sec to stat 23K files from an SSD? Marc MERLIN
2012-08-01  6:08           ` Fajar A. Nugraha
2012-08-01  6:21             ` Marc MERLIN
2012-08-01 21:57               ` Martin Steigerwald
2012-08-02  5:07                 ` Marc MERLIN
2012-08-02 11:18                   ` Martin Steigerwald
2012-08-02 17:39                     ` Marc MERLIN
2012-08-02 20:20                       ` Martin Steigerwald
2012-08-02 20:44                         ` Marc MERLIN
2012-08-02 21:21                           ` Martin Steigerwald
2012-08-02 21:49                             ` Marc MERLIN
2012-08-03 18:45                               ` Martin Steigerwald
2012-08-16  7:45                                 ` Marc MERLIN
2012-08-02 11:25                   ` Martin Steigerwald
2012-08-01  6:36           ` Chris Samuel
2012-08-01  6:40             ` Marc MERLIN
2012-08-01  8:18         ` du -s src is a lot slower on SSD than spinning disk in the same laptop Spelic
2012-08-16  7:50         ` Marc MERLIN
     [not found]           ` <502CC2A2.4010506@shiftmail.org>
2012-08-16 17:55             ` Marc MERLIN
2012-09-05 16:52               ` ext4 crash with 3.5.2 in ext4_ext_remove_space Marc MERLIN
2012-09-05 17:50                 ` Lukáš Czerner
2012-09-05 17:53                   ` Marc MERLIN
2012-09-06  4:24                   ` Marc MERLIN
2012-09-07 15:19                     ` Marc MERLIN
2012-09-07 15:39                       ` Lukáš Czerner
2012-09-07 15:51                         ` Marc MERLIN

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