keep cyrus in sync with cold standby

[Adam Tauno Williams]

On Tue, 2012-10-16 at 17:26 +0200, Marcus Schopen wrote:
> I'm thinking about a strategy to keep my cyrus server (2.2.13 on Ubuntu
> 10.04 LTS) in sync with a cold standby server. This hasn't to be a
> live/hot sync and I'd like to keep it as simple as possible. A sync
> delay up to 30 minutes is acceptable for this small setup (250 Accounts,
> 80 GB mail storage, 5 emails per minute), but I don't want to stop cyrus
> while doing the snyc.
> Cyrus replication seems to be the most reasonable way, but I'm sitting
> on Ubuntu 10.04 LTS, which comes with cyrus 2.2.13 and I can't find any
> newer backports. Centos 6.x with Cyrus 2.3.16 could be an alternative
> setup, but I'm not sure if 2.3.16 is also to old for stable
> replication. :/

Late 2.3.x [including 2.3.16] were stable.  And the replicate worked.

I'd just use Cyrus' replication.  That way you know you have a
consistent replicate - and you can authenticate to the replica and check
on it if you want, see that "yep, it is the same".   Other alternatives
provide a backup you *believe* is good, but you don't know until you try
it, and then you find out it is busted.

> DRBD could be an option but I never had DRBD running within a parallels
> virtualisation (bare metal setup); might be a timing/performance problem
> with a lot of very small files?
> Do I run in bad problems if I just run a simple rsync
> of /var/lib/cyrus, /var/spool/cyrus/ and /var/spool/sieve/ and dump
> mailboxes.db (skiplist) with "ctl_mboxlist -d" every 30 minutes? Is
> there a way give cyrus a flush of its databases without stopping it?

rsync will work, but if it is against a live instance you may need to
reconstruct before you bring it back up.  It will work 99.44% of the
time but it can be time-consuming and is just adding another step.