Re: High Availability / Clustering

[Dave Augustus <davea@support.kcm.org>]

Hi Lee,

Here is another twist that provides load-balancing and failover for
writes:

I have LDAP slaves available for reads via Linux Virtual Server(LVS).
Any servers that require LDAP look at the LVS IP address for
information.

Then I have 2 additional machines runing in a master/slave situation via
hearbeat- they share a common IP. When the master(server A) goes down (
for whatever reason) the slave(server B) is promoted. When the original
master(server A) comes up again, it comes up as a slave and then
determines via heartbeat if it needs to promote itself to be the master
again. Any writes and occured while it was offline are attemped by the
slurpd running on the new master (server B) or are available via the
replog.rej files.

It is all just a matter of some scripts, heartbeat and Openldap. This
system has been in production for 6 months and works great!

Dave Augustus

On Thu, 2003-04-10 at 16:47, Lee wrote:
> Ive read through most of the archives concerning high-availability 
> options for openldap. Right now, we're trying to create make our ldap 
> infrastructure highly-available, as well as load-balanced between three 
> servers (more to be added later). From my research it seems like we 
> have a few options:
> 
> 1) Experimental Multi-Master: This seems to have a number of atomicity 
> issues. Plus this doesn't really solve the problem with the ldap 
> clients not appropriately using the second listed server if the first 
> goes down.
> 
> 2) Plain old Master + Multiple Slaves: Same second issue above, plus no 
> high availability on writes.
> 
> 3) Master + Slaves, Promotion of Slave if master goes down: Same ldap 
> client not using second listed server problem as in 1) and 2) above, 
> plus lots of issues with reclaiming Master status after failure.
> 
> 4) 1 Master Server Cluster using shared storage: This seems like the 
> only viable solutions. The problem is we need support for many servers 
> connecting to one shared storage device, as well some sort of reliable 
> locking mechanism thats compatible with openldap.
> 
> Has anyone successfully implemented 4) ? If so can you recommend any 
> specific hardware and or software that works nicely with openldap?
> 
> 
> Thanks,
> L