Using Replication For High Availability - Red Hat DIRECTORY SERVER 7.1 - DEPLOYMENT Deployment Manual

There are performance issues to consider for both the Directory Server and the
efficiency of the network connection:
• Where replication is performed across a public network such as the Internet,
the use of SSL is highly recommended. This will guard against eavesdropping
of the replication traffic.
• You should use a T-1 or faster Internet connection for your network.
• When creating agreements for replication over a wide-area network, it is
recommended that you do not keep your servers always in sync. Replication
traffic could consume a large portion of your bandwidth and slow down your
overall network and Internet connections.
• When initializing consumers, do not to initialize the consumer immediately;
instead, utilize filesystem replica initialization, which is much faster than
online initialization or initializing from file. See the Red Hat Directory Server
Administrator's Guide for information on using filesystem replica initialization.

Using Replication for High Availability

Use replication to prevent the loss of a single server from causing your directory to
become unavailable. At a minimum, you should replicate the local directory tree to
at least one backup server.
Some directory architects argue that you should replicate three times per physical
location for maximum data reliability. How much you use replication for fault
tolerance is up to you, but you should base this decision on the quality of the
hardware and networks used by your directory. Unreliable hardware needs more
backup servers.
NOTE You should not use replication as a replacement for a regular data
backup policy. For information on backing up your directory data,
refer to the Red Hat Directory Server Administrator's Guide.
If you need to guarantee write-failover for all you directory clients, you should use
a multi-master replication scenario. If read-failover is sufficient, you can use
single-master replication.
LDAP client applications can usually be configured to search only one LDAP
server. Unless you have written a custom client application to rotate through LDAP
servers located at different DNS hostnames, you can only configure your LDAP
client application to look at a single DNS hostname for a Directory Server.
Defining a Replication Strategy
Chapter 6 Designing the Replication Process 129