From: Theodore Tso <tytso@MIT.EDU>
To: Alberto Bertogli <albertito@blitiri.com.ar>
Cc: dm-devel@redhat.com, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: jbd2 inside a device mapper module
Date: Fri, 26 Dec 2008 13:06:42 -0500 [thread overview]
Message-ID: <20081226180642.GO9871@mit.edu> (raw)
In-Reply-To: <20081226161708.GC4127@blitiri.com.ar>
On Fri, Dec 26, 2008 at 02:17:08PM -0200, Alberto Bertogli wrote:
>
> At this moment I'm trying to keep it simple, so I plan to batch two for
> each sector written to the device: one for the metadata and one for the
> data.
>
I think I can pretty much guarantee that your performance will be so
horrible that it won't be worth using.
> > Yes, this is necessary because in a production system you need to be
> > able to identify the external journal by UUID, and the ext2/3/4
> > superblock makes it easy to add a label, UUID, et. al. It also
> > significantly lowers the chance that an external journal will get
> > misidentified as some other filesystem based on the data stored in the
> > journal.
>
> Yes, it makes sense. I've reserved the first sector for that purpose.
Why not just use the ext3/4 external journal format?
- Ted
WARNING: multiple messages have this Message-ID (diff)
From: Theodore Tso <tytso@MIT.EDU>
To: Alberto Bertogli <albertito@blitiri.com.ar>
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
dm-devel@redhat.com
Subject: Re: jbd2 inside a device mapper module
Date: Fri, 26 Dec 2008 13:06:42 -0500 [thread overview]
Message-ID: <20081226180642.GO9871@mit.edu> (raw)
In-Reply-To: <20081226161708.GC4127@blitiri.com.ar>
On Fri, Dec 26, 2008 at 02:17:08PM -0200, Alberto Bertogli wrote:
>
> At this moment I'm trying to keep it simple, so I plan to batch two for
> each sector written to the device: one for the metadata and one for the
> data.
>
I think I can pretty much guarantee that your performance will be so
horrible that it won't be worth using.
> > Yes, this is necessary because in a production system you need to be
> > able to identify the external journal by UUID, and the ext2/3/4
> > superblock makes it easy to add a label, UUID, et. al. It also
> > significantly lowers the chance that an external journal will get
> > misidentified as some other filesystem based on the data stored in the
> > journal.
>
> Yes, it makes sense. I've reserved the first sector for that purpose.
Why not just use the ext3/4 external journal format?
- Ted
next prev parent reply other threads:[~2008-12-26 18:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-24 21:10 jbd2 inside a device mapper module Alberto Bertogli
2008-12-24 22:38 ` Alberto Bertogli
2008-12-24 23:49 ` Theodore Tso
2008-12-25 14:35 ` Alberto Bertogli
2008-12-25 15:52 ` Theodore Tso
2008-12-25 15:52 ` Theodore Tso
2008-12-26 0:00 ` Alberto Bertogli
2008-12-26 3:37 ` Theodore Tso
2008-12-26 3:37 ` Theodore Tso
2008-12-26 16:17 ` Alberto Bertogli
2008-12-26 18:06 ` Theodore Tso [this message]
2008-12-26 18:06 ` Theodore Tso
2008-12-27 3:00 ` Alberto Bertogli
2008-12-27 19:29 ` Theodore Tso
2008-12-27 19:29 ` Theodore Tso
2008-12-29 21:30 ` Alberto Bertogli
2008-12-27 20:01 ` Andreas Dilger
2008-12-29 6:20 ` Shyam_Iyer
2008-12-29 6:20 ` Shyam_Iyer
2008-12-29 21:05 ` [dm-devel] " Alberto Bertogli
2008-12-30 6:55 ` Alex Tomas
2008-12-30 13:51 ` Alberto Bertogli
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