Administration Guide › Set Up Replication › Types of Replication Supported on CA Directory

Types of Replication Supported on CA Directory

CA Directory supports the following methods of replication:

Multiwrite

Multiwrite replication is a mechanism for replicating updates to a number of DSAs to ensure that they are synchronized. When a DSA receives an update, it updates its own data and then sends the update to its peers. If a peer DSA cannot be reached, the updates are queued and replayed when the DSA becomes available.

DISP

DISP (Directory Information Shadowing Protocol) is defined in the 1993 X.525 standard. DISP lets you replicate information in OSI-conformant directories, which permits copying of directory information from one DSA to another using a standardized procedure and protocol.

Multiwrite replication with DISP recovery ('Multiwrite-DISP')

Multiwrite-DISP replication is a replication scheme that uses multiwrite replication for real-time updates and DISP for recovery.

Multiwrite and DISP have complementary strengths: multiwrite replays updates to another DSA, and is fast and secure for small differences. However, if multiwrite has more updates to be replayed to another DSA than it can fit in its queue, it stops using the queue and drops all update information for that DSA. This means that multiwrite replication cannot cope with a DSA being down indefinitely. By contrast, DISP compares the current states of two DSAs and can handle a DSA being down indefinitely.

Multiwrite-DISP is the recommended method of replication with CA Directory because it combines the efficiency of multiwrite when DSAs are online, with the robustness of DISP to allow DSAs to recover after being offline.