Subject: Re: [vserver] Poll: High (ish) availability - how are you doing it?
From: Gordan Bobic <gordan@bobich.net>
Date: Tue, 27 Jul 2010 16:34:30 +0100

On Tue, 2010-07-27 at 17:29 +0200, Remigiusz Modrzejewski wrote:
> On Jul 27, 2010, at 16:32 , Gordan Bobic wrote:
> > 
> >> I would be interested in any systems 
> >> people have experienced that do an async replication between two 
> >> machines, eg some process which uses inotify/dazuko/redirfs to watch for 
> >> changes and then an async queue to merge changes to the second machine - 
> >> the goal being to have a near realtime replica, but without the 
> >> performance penalty associated with cluster filesystems?
> > 
> > It sounds like you are looking for lsyncd.
> > 
> > [...]
> >> A more satisfactory solution seems to be active-active clustering.  This 
> >> is now irrelevant to linux-vserver, but does anyone here have any 
> >> experience of running active-active clusters of mailservers, webservers, 
> >> etc?
> 
> 
> Well, an excerpt from the front page of lsyncd reads:
> 
> #v+
> When not to use:
> 
> File with active file handles (e.g. database files) Directories where many changes
occur (like mail or news servers)
> 
> In these cases e.g. DRBD (see http://www.drbd.org) might be better for you.
> #v-
> 
> So if the OP is planning to use it for mail servers, lsyncd may not be a good idea.
Anyhow thanks
> for pointing it :)

You're welcome. :)
You are forgetting, however, is that the OP also mentioned using rsync
for keeping things in sync, and lsyncd is a least a slightly cleaner
solution that rsyncing the whole machine in a cron job.

Gordan