Backing Up and Restoring Novell eDirectory
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For fault tolerance during normal business circumstances, they have created three replicas of each
partition of their tree, so that if one server is down, the objects in the partitions it holds are still
available from another server. They have also planned for recovery of individual servers by backing
up all their servers regularly with the Backup eMTool, turning on roll-forward logging, and storing
the backup tapes at a remote location.
For disaster recovery planning, Delores and her team have also designated two of their servers as
DSMASTER servers. They use two servers because their tree is large enough that more than one
DSMASTER server is needed to hold a replica of every partition. Every partition in the tree is
replicated on one of the two DSMASTER servers. Neither of the two DSMASTER servers hold
replicas of the same partition, so there is no overlap between them. This design is an important part
of their disaster recovery plan.
In their test lab, Delores and her team periodically test the backups to make sure their backup
strategy will meet their goals.
One night the Human Resources Consulting, Inc. building is damaged by a hurricane, and all the
servers in the data center are destroyed.
After this disaster, Delores and her team first restore the two DSMASTER servers, which hold
replicas of every partition. They use the last full backup and the subsequent incremental backups,
but can't include roll-forward logs in the restore because they were lost when the servers were
destroyed. Delores and her team planned the DSMASTER servers so that they don't share replicas.
Because the two DSMASTER servers do not share replicas, the restore verification process is
successful for both servers even though the roll-forward logs are not part of the restore. After the
DSMASTER servers are restored, all the objects in the tree for Human Resources Consulting, Inc.
are now available again.
The DSMASTER servers are important because Delores and her team can use them to re-create the
tree without inconsistencies after a disaster.
They were using roll-forward logs so they could restore a server to the state it was in at the moment
before it went down, bringing it back to the synchronization state expected by other servers in the
replica ring. This allows the server to resume communication where it left off, and receive any
updates it needs from the other replicas to keep the whole replica ring in sync.
However, in this disaster situation, Delores and her team do not have the roll-forward logs. Without
the roll-forward logs, only one server in a replica ring can be restored without errors—the first one
they restore. For the rest of the servers, the restore verification process will fail because the
synchronization states don't match what the other servers expect (see
“Transitive Vectors and the
Restore Verification Process” on page 423
). If the restore verification fails, the restore process will
not activate the restored eDirectory database.
Delores and her team anticipated this, and they have planned for it. They use the two DSMASTER
servers as a starting point, which gives them only one replica of each partition.Those servers can be
restored without verification errors, and then the replicas they hold can be used as masters to be
copied onto all the other servers.
After restoring the DSMASTER servers, restoring the rest of the servers requires some extra steps.
Delores and her team must restore each of the remaining servers by doing the following:
Making sure that the replicas on the DSMASTER servers are designated as master replicas.
Removing all the servers except the DSMASTER servers from the replica rings.
Restoring the full and incremental backups for each of the other servers.
Summary of Contents for EDIRECTORY 8.8 SP2
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