Begin using a metapartition on existing system?

[Bron Gondwana]

On Fri, Oct 15, 2010 at 05:02:36PM -0500, Scott Lambert wrote:
> I'm not doing well with my Google-foo.
> 
> I initially setup our first Cyrus-IMAPd system recently.  I had a
> conceptual misunderstanding and thought that the config directory
> could be configured to hold the metadata.  Actually, I thought it
> would happen by default.  I don't know what I was thinking.
> 
> Now that I have that sorted out in my head, and we are out of I/O
> bandwidth, I want to configure a metapartition-default on a new
> RAID1 and move the metadata to it.  I haven't been able to find
> documentation that says if it is safe to add the metapartition
> directives to the config for an existing partition on a running
> system.
> 
> What would be the proceedure for this?  Something like?:
> 
>   * rsync the metapartition_files to the new metapartition-default
>   * shut down cyrus-imapd
>   * rsync the metapartition_files to the new metapartition-default
>   * change the imapd.conf 
>   * remove the metapartition_files from partition-default
>   * start cyrus-imapd
> 
> I would like to do it without stopping cyrus-imapd, but I suspect
> that changing it on a running system was not planned for in the
> feature.  I would be most happy to be wrong.

You'll find you are definitely right.  You'll have to shut it down.

You can make it a lot shorter by moving the 'start cyrus-imapd'
before the 'remove the metapartition_files from partition-default'
step.  Cyrus won't mind about the spare files being there.

But doing it on the fly - ouch.  Definitely not designed for.
It probably wouldn't be a massively hard problem to solve, but
it's such a rare case that nobody much cares enough to make it
work.

Regards,

Bron.