Re: OpenLDAP Servers and Availability

[Aaron Richton <richton@nbcs.rutgers.edu>]

> I want to set up openldap servers to be available all the time.

Don't we all.

> I looked at Master-Slave with Syncrepl and Multi-master configurations. I
> don't understand which configuration could help me.

Master-Slave means that you have one master that will handle writes, and 
arbitrary n slaves that will handle reads. Multimaster means that you have 
an arbitrary n masters that will handle writes, and arbitrary n slaves 
that will handle reads. It depends on your particular requirements which 
one you go with; the benefits and drawbacks of both have been discussed at 
length on this list, so go through the archives.

> Also, how would I test my requirement?

A simple method would be to set up a testbed with the desired 
configuration, and use clients such as OpenLDAP's ldapsearch and 
ldapmodify to generate load. A simple method to simulate failure is 
pulling the Ethernet cable (then try running those same clients to make 
sure things converged nicely).

> Is it possible to set up highly available openLDAP servers? Please suggest.

I seriously can't remember the last time I turned off all my slaves. It 
has probably never happened. I'm not even sure that I took a visible 
downtime when I went 2.2 -> 2.3. I can't see why I would for 2.3 -> 2.4.

(Not that my machines don't die or anything like that. But they're load 
balanced, so I don't need to panic when they do.)