Re: [linux-lvm] Reiserfs, 2.4.7, snapshots w/ 0.9

["Heinz J . Mauelshagen" <mauelshagen@sistina.com>]

Mark,

Chris Mason implemented an interface between the VFS and LVM, which is defined
by 2 new functions VFS functions. They have to be supported in the filesystem
itself in order to flush the journal and lock the filesystem for I/O, get
back to LVM so that it can activate the prepared snapshot. LVM unlocks the
filesystem after this.
You pay a (small) I/O penalty for the journal flush.

Because those functions are not in vanilla, you still need to patch the
kernel with the linux-2.4.X-VFS-lock-patch contained in the LVM distribution :-(

That patch will enable the above feature after a kernel recompile/reboot.


On Wed, Jul 25, 2001 at 10:36:40AM -0500, Mark Bainter wrote:
> I'm using LVM on a couple of our production systems, and I'm very 
> happy with it.  It's been working very well for us.  However, we
> have a very large database and backing it up has become problematic.
> 
> So, naturally, I began looking into using LVM's snapshot feature. 
> The filesystem the database rests on is a reiserfs partition.  
> Creating the snapshot volume (acc to the directions in the howto) 
> works fine, but when I try to actually mount it I get:
> 
> $ sudo mount -t reiserfs -oro /dev/main/db_backup /mnt/dbbackup 
> mount: wrong fs type, bad option, bad superblock on /dev/main/db_backup,
>        or too many mounted file systems
> 
> checking dmesg reveals:
> reiserfs: checking transaction log (device 3a:04) ...
> clm-2076: device is readonly, unable to replay log
> Replay Failure, unable to mount
> reiserfs_read_super: unable to initialize journal space
> 
> Ok, so I did some searching and found some people back in the first
> part of this year had a similar problems but none of the solutions
> really applied to me fwict.  They all appeared to be using a 
> previous version of the kernel, or of the lvm code.  I looked through
> the changelog and did see a few notations of fixes since 0.9 related
> to the snapshot code.  But, I'm kind of wary about putting a beta 
> on my production systems with something this critical, w/out knowing
> for sure that it will fix the problem.
> 
> So, is the problem in lvm?  reiserfs?  Or is it just me?  Is there
> any other information I can give that might be helpfull in figuring
> out the problem?  Just let me know. 
> 
> TIA
> _______________________________________________
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> linux-lvm@sistina.com
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> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
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