Cyrus crashed on redundant platform - need better availability?

[Jure Pečar]

On Wed, 15 Sep 2004 13:38:43 +0200
Paul Dekkers <Paul.Dekkers at surfnet.nl> wrote:

> But I suppose RH's cluster manager takes care of mounting the partitions 
> and checking them if there are any errors.

Not really, at least not by itself. See
http://people.redhat.com/jrfuller/cms/ for detailed documentation of what is
included with RH AS 2.1 (it's some $500 extra for AS 3).
I had to write some pretty paranoid scripts that take care of assembling
software raids, checking the fs and mountig it while taking care about the
other machine to prevent problems.

Of course all this would be much easier with some kind of clustered fs, but
clustered fs brings a new problem: locking. Almost all i've seen so far have
an external 'locking manager' on a separate box, which brings ethernet
latency into every lock operation, which i'm sure is very noticable in the
lock-heavy usage patterns as mail is. But this is just my feeling, i haven't
yet benchmarked any :)

> Do you think using RH's cluster software is a valuable consideration for 
> this kind of clustering setup? Using FreeBSD there are not that many 
> clustering solutions for now, and if it's advisable to at least consider 
> using RH here (although I have no experience with RH) we can certainly 
> look at it. (Any idea how fast RH would "recover services"?)

This RH cluster software is nothing fancy; i'm sure equivalents exists for
BSDs. See documentation link above. Actually it is just Kimberlite
(http://oss.missioncriticallinux.com/projects/kimberlite/), sold with RedHat
support.
"Speed" of recovery is almost completely out of the cluster control. The
only thing that matters for the cluster is what your cyrus init script
returns when called with 'status' parameter. Everything else is up to your
init scripts.
Of course, if one box dies completely, the other takes over in the
configurable time.


-- 

Jure Pečar
---
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