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/
next prev parent reply other threads:[~2012-02-12 22:32 UTC|newest]
Thread overview: 52+ 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
[not found] ` <20120801053042.GG12695@merlins.org>
2012-08-01 6:01 ` 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
2012-02-18 16:07 ` brtfs on top of dmcrypt with SSD. No corruption iff write cache off? Marc MERLIN
2012-02-19 0:53 ` Clemens Eisserer
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