Fwd: Docs for Cyrus/GFS?

[Chris St. Pierre]

Jens--

Thanks for your help!  I've been able to get Cyrus IMAP running now
with a shared backend, and my tests thus far indicate that it's
working dandy.

It looks like most of the "important" databases are already skiplists;
the only ones that defaulted to BDB were the duplicate, tlscache, and
ptscache databases.  What, if anything, do I need to do special when
converting my data over?  I'll not be changing Cyrus versions; will it
"just work" to move all of my current data, or will I need to convert
databases/reconstruct/etc.?

Thanks again!

Chris St. Pierre
Unix Systems Administrator
Nebraska Wesleyan University

On Mon, 8 Sep 2008, Jens Hoffrichter wrote:

> There I told him to write to the list, and I just clicked the wrong
> reply button myself ;)
>
> Sorry for that.
>
>
> ---------- Forwarded message ----------
> From: Jens Hoffrichter <jens.hoffrichter at gmail.com>
> Date: 2008/9/8
> Subject: Re: Docs for Cyrus/GFS?
> To: "Chris St. Pierre" <stpierre at nebrwesleyan.edu>
>
>
> Hi Chris,
>
> 2008/9/8 Chris St. Pierre <stpierre at nebrwesleyan.edu>:
>
>> I'm looking for any good documentation on using Cyrus IMAP with shared
>> storage (in our case, GFS).  Thus far, all I've been able to turn up
>> is a few snippets on mailing lists and in the wiki, but nothing really
>> comprehensive.  Any pointers?  Thanks!
> There is no real documentation up to now, I think, but I'm in the
> process of implementing a quite big mail system on top of a GFS, so if
> you have any specific questions, just ask here on the list or me
> directly, though on the list would probably be better, to share the
> answers.
>
> Just some hints for things I stumbled upon up to now:
>
> I suppose you meta directory will be shared, so you need to separate
> out some directories between the single nodes, where each node can put
> its own files. Directories coming to my mind are "proc" and "backup".
> There are probably some more, but I have no access to the machine
> right now to check it. For the separation there I used the named
> symlinks from GFS, which worked quite fine.
>
> The other thing is: Make ABSOLUTELY sure that you turn off anything
> related to bdb during compile (you probably need to compile your own
> cyrus anyway, we are using the incova sources here), as berkeley db
> just doesn't work on top of GFS. Or, at least not in a cyrus context.
> And it isn't sufficient to just use skiplist in the config file, you
> definitely need to switch off compiling bdb support.
>
> The reason for this is that even if you don't have any bdbs
> configured, cyrus will still initialize some sort of bdb environment
> in your meta directory, and if on another sort the same thing is
> happening during the same time, it will try to sleep on a mutex,
> waiting for the release of the mutex. Yet, the callback to wake up
> never comes when using GFS, so your process will hang indefinitely.
> That one took us at least 3 weeks to figure out ;)
>
> Besides from those little things, cyrus works on top of the GFS just
> fine, you probably need to tweak some tuning parameters, but I don't
> remember them right now, if you need them, I can look them up for you.
>
> The performance is nothing to brag about, though, cyrus and GFS just
> don't play that well together. But I got the performance I needed
> (around 15 logins per second with three nodes using a loadbalancer),
> which is sufficient for our needs. The added reliability is nice,
> though, as you can turn off one node, and the whole thing still works.
>
> I don't know if you have any experience using RedHat Cluster, but be
> absolutely sure to understand about fencing and quorum of the cluster
> before you start any configuration. Cluster software is by no means
> really easy to use, IMO, and everything you do needs some extra
> thinking if you are just used working with single nodes normally :)
>
> Just try your luck, and if you have any questions, just ask.
>
> Jens
> ----
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>