Re: Re[4]: openldap-server-2.2.29: multimaster support

["John Madden" <jmadden@ivytech.edu>]

> Some of your customers may have been tricked into believing they need
> LB.  If you mean LB on writes, that IS PURE NONSENSE.  The number of
> writes on each of the servers (either masters or slaves) will ever be
> the same no matter how many write entry points you provide (unless you
> believe replication writes are inexpensive; they are not).  If you mean
> LB on reads, I don't see how so-called multimaster could help you there
> more than a single master with an appropriate number of slaves can.

And furthermore, load-balancing clients across slaves isn't technically correct --
two clients can still pull different versions of the same object at the same time
if they hit two different slaves (that's what multi-master is "supposed" to fix).

This is analagous to the whole SQL database clustering problem that Oracle RAC
(for example) serves to fix.  A client can connect, grab some data, and because of
RAC's distributed lock mechanism, can be guaranteed that it isn't being written to
at that time someplace else in the cluster.  IMO, any multi-master would need the
same sort of communication and agreement among the nodes.

John



-- 
John Madden
UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@ivytech.edu