Re: High availability

[Buchan Milne <bgmilne@staff.telkomsa.net>]

On Sunday 12 August 2007 19:51:39 Dmitriy Kirhlarov wrote:
> Taymour A. El Erian wrote:
> > Hi,
> >
> > I have been searching for a long time to find a solution to give me
> > high availability on the writing. We have 2 ldap servers running as
> > multi master (I know it is not considered a good thing and it is very
> > old 2.0.x), this way if one is down the other will accept writes
> > (add/modify/delete). If we do the normal single master multiple
> > slaves, we will get more performance and high availability for reads
> > but if the master is down no updates. Also, we can not separate writes
> > from reads and we can not use referrals (not all applications we have
> > can chase referrals). I though of having a standby master and use
> > heartbeat but it doesnt look like a stable solution, any ideas ? maybe
> > shared disk ?
>
> For openldap 2.{2,3}.x you can use ggated+gmirror+carp (on freebsd) or
> heartbeat + mirror with drdb (on linux). It should work.

Or any clustering system using shared storage. For example, I have a cluster 
running RHEL3 with Red Hat Cluster Suite on (shared) Fibre-attached storage.

In the end, there isn't that much that is specific to OpenLDAP (e.g. most 
clustering solutions provide support for MySQL, the only difference is which 
init script the clustering middleware uses to start/stop the service).

> For openldap 2.4 two-node multi-master solution declared, afaik, but
> currently 2.4 is alpha.

But, for some applications (which just like to assume that one IP address will 
always have the master), you may still need a load balancer or clustering 
software to manage a virtual IP address to get the HA part ...

Regards,
Buchan