Quoting Mike Jackson <mj@xxxxxx>:
Hi Pierangelo,
The fact that LDAP directory servers are not intended to support a
high frequency of write operations means that the term "write load
balancer" is not the correct term to use when describing the benefits
of multi-master versus single-master replication - unless you are
arguing how to support systems architects who intentionally (or
perhaps out of ignorance) use LDAP technology in an incorrect manner
in their designs. The correct term to use in this context, IMO, is
"highly available write operations".
I thought that more accurately describes it as well. And my approach would be
to have a "primary" master and a "secondary" master. Throw all your writes at
your primary master and if they all go through there, no need to worry about
consistency. In the event of a disaster, the secondary master is quite
capable
of taking the writes as well and keeping things running. This is almost akin
to your master/promotable slave concept, except the promotable slave is not
really a slave but a standby master. If you're concerned about load, throw in
a bunch of slaves that are read-only and point your read-only lookups at the
slaves, reserving your masters for applications that need write access.
End result - highly available write operations, that minimize consistency
issues. Highly available read operations. It requires intelligent
design of a
directory infrastructure, as you note - sometimes I think we expect
software to
design that too :)
Kevin
--
Kevin M. Myer
Senior Systems Administrator
Lancaster-Lebanon Intermediate Unit 13 http://www.iu13.org
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