Table of Contents
Advertisement
These decisions cannot be made effectively without an understanding of how the
Directory Server handles these concepts. For example, when you decide what
information you want to replicate, you need to know what is the smallest
replication unit that the Directory Server can handle. The following sections
contain definitions of concepts used by the Directory Server. This provides a
framework for thinking about the global decisions you need to make.
Unit of Replication
In Directory Server 6.0, the smallest unit of replication is a database. This means
that you can replicate an entire database, but not a subtree within a database.
Therefore, when you create your directory tree, you must take your replication
plans into consideration. For more information on how to set up your directory
tree, refer to Chapter 5, "Designing the Directory Topology."
The replication mechanism also requires that one database correspond to one
suffix. This means that you cannot replicate a suffix (or namespace) that is
distributed over two or more databases.
Read-Write Replica/Read-Only Replica
A database that participates in replication is defined as a replica. There are two
kinds of replicas: read-write or read-only. The read-write replicas contain master
copies of directory information and can be updated. Read-only replicas refer all
update operations to read-write replicas.
Supplier/Consumer
A server that holds a replica that is copied to a replica on a different server is called
a supplier for that replica. A server that holds a replica that is copied from a
different server is called a consumer for that replica. Generally, the replica on the
supplier server is a read-write replica, and the one on the consumer server is a
read-only replica. There are exceptions to this statement:
•
In the case of cascading replication, the hub supplier holds a read-only replica
that it supplies to consumers. For more information, refer to "Cascading
Replication," on page 103.
•
In the case of multi-master replication, both masters are suppliers and
consumers for the same read-write replica. For more information, refer to
"Multi-Master Replication," on page 101.
In Directory Server 6.0, replication is always initiated by the supplier server, never
by the consumer, in contrast to earlier versions of the Directory Server that allowed
consumer-initiated replication (where you configure consumer servers to pull data
from a supplier server).
Introduction to Replication
Chapter 6
Designing the Replication Process
97
Advertisement
Table of Contents
