upgrade 2.2.x -> 2.3.x, sync repl replica compatibility?

[Jed Donnelley <jed@nersc.gov>]

OpenLDAP,

We run an OpenLDAP master with some 5-6 sync repl replicas.  Several 
of our replicas are on clusters with only loosely coupled 
administration.  Currently all these servers (master and slaves) 
still run some versions of OpenLDAP 2.2.x.  We would very much like 
to upgrade to 2.3.x as we've had some stability problems with the 
2.2.x servers.

What I'm not sure about is how to go about the upgrade.  All these 
servers are compiled from source, so there's no problem upgrading 
them individually.  However, it would be a serious problem trying to 
synchronize upgrading all of them at once.

Does anybody have any experience or might be able to tell me or point 
me to docs (which I failed to find) if there's an upgrade path (e.g. 
master first, slaves first, any order OK) that can avoid having to 
restart all these servers simultaneously on the new software?

--Jed http://www.nersc.gov/~jed/