Re: [Linux-cluster] IMAP server clustering ...

[Lon Hohberger <lhh redhat com>]

On Thu, 2004-10-28 at 13:14 -0600, Michael Gale wrote:

> 2. GFS does not protect against data corruption as it is the 
> applications responsibility to making sure that data written to a file 
> is complete.

> 3. Maildir format does not require file locking and works great over NFS 
>   except for the speed issue of course.

"Not requiring file locking" is not the same as "not requiring any
locking".

> If you use Courier IMAP every body can access the same directories / 
> partitions at the same time because file locking is not an issue.
> "IMAP_USELOCKS
> 
>      This setting in /usr/lib/courier/etc/imapd must be enabled. This 
> setting uses dot-lock files to synchronize updates to folder indexes 
> between multiple IMAP clients that have the same folder opened.

>      This setting is safe to use with NFS, as it does not use actual 
> file locking calls, and does not require the services of the problematic 
> NFS lock"

Instead of file locking, they're doing dot-locking.

I suspect GFS would work fine if you had the above setting enabled;
creating a file (e.g. a dot-lock) should be atomic across the cluster.

-- Lon