Re: [RFC] ext3 multi-mount protection

On Wed, Jul 12, 2006 at 03:03:39PM -0600, Andreas Dilger wrote:
> Is there any ext3/ext4 interest in a mechanism for protecting ext3/ext4
> filesystems from being mounted concurrently by multiple nodes on a SAN
> at the same time?
> 
> We often run the ext3 server filesystems in an HA configuration so that
> there are two servers on a FC switch that can access the same shared
> disk.  Sadly, HA software is far from reliable and this can sometimes
> lead to both servers trying to access the same device at one time.
> This is true if you are using ext3 for HA NFS serving, or other non-HA
> setups where the same disks are accessible by multiple nodes (regardless
> of whether they are _supposed_ to touch those disks or not), because the
> ext3 journal recovery can corrupt the filesystem even if mounted read-only,
> or if some clueless sysadmin tries to mount or use "those unused disks".
> 
> We've developed a small patch for ext3 to prevent the filesystem from
> being mounted concurrently on two nodes.  Is there general interest in
> this becoming part of ext3/ext4?

I too have come across a situation where this has been a problem in a
customer environment, so yes, this seems like a useful feature to me. Could
you send out the patch - I'm curious to understand how it works.

Regards
Suparna

> 
> Cheers, Andreas
> --
> Andreas Dilger
> Principal Software Engineer
> Cluster File Systems, Inc.
> 
> 
> 
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-- 
Suparna Bhattacharya ([email protected])
Linux Technology Center
IBM Software Lab, India



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