Cyrus, clusters, GFS - HA yet again

[Janne Peltonen]

Hi, and thanks for the answer.

On Sun, Oct 29, 2006 at 09:11:53PM -0500, Wesley Craig wrote:
> On 27 Oct 2006, at 03:35, Janne Peltonen wrote:
> >Or should I just give up and start considering Murder?
> Before you decide on whether to give up on clustering, you should  
> thoroughly consider Murder.  At a minimum, it provides the location  
> independence that you'd like.  With replication, you have a  
> realistic, immediate recovery path for machine failure.  Both of  
> those are much better than what you have, while not as good as a real  
> HA system.  But murder + replication will be a lot less work than  
> developing an HA architecture from scratch.

It is very true that building an HA architecture from scratch is a lot
of work. But I'm not really trying to build it from scratch: I'm trying
to recreate with Linux and RedHat GFS an architecture that's been in
production use with Tru64 and its cluster FS (in Ohio), or with some
other *nix and Veritas (in Pittsburgh).

There were a couple of reasons I wanted to try this solution before
Murder, replication and friends. The main reason was, if this could be
get to work, it would have a lot less moving parts than Murder: no need
for differently configured front and back end cyrus servers; no need for
a MUPDATE master server. Each server could be more or less identical,
and if one of them went down, there would be no loss of service (ok, the
load-balancing box would have to notice that one of the ip addresses it
shares went away, and the active imap connections to the dead server
would die, but that's it, really). And adding a new server to the pool
could be almost as easy as putting a new HP Blade on the rack,
configuring its MAC in our DHCP server, installing an HD image on its
local HD, booting it, and configuring its IP on the IP-sharing box.

Of course, if it won't work, it won't work, and Murder is the supported
solution. When my predecessor made his decision on what solution to
pursue, he considered Murder much too complicated, and wasn't sure
whether 2.3 was mature enough (that is, replication and friends), but
this all might have changed - and he might have been wrong even then. ;)

But then, other people seem to have got this to work - or something very
similar. The simplicity of the setup is so appealing that I'd really
like to give it a try.


Regards,
--Janne