Chapter 21. Replication and disaster recovery overview 335
ProtecTIER V3.2 and later (machine 3958-DD5) supports native replication in all available
functional modes:
򐂰 Virtual Tape Library (VTL)
򐂰 OpenStorage (OST)
򐂰 File System Interface (FSI)
21.2 Disaster recovery operations
Disaster recovery is the process of recovering production site data in a DR location. Disaster
recovery is useful if a disaster occurs or a situation occurs where the production (or primary)
site goes offline. The hub, or DR site, can take the place of the production site until the
primary site comes back online. When the primary site comes back online, previously
replicated and newly created tapes can be moved to the main production site using the
failback process. The primary site then resumes its roll as production and primary site for
the user.
When the user enters the ProtecTIER Disaster Recovery (DR) mode, all incoming replication
and visibility switching activities from the failed production site to the DR site (hub) are
blocked. When that primary site is rebuilt or replaced, the user can then return the data to that
primary site and continue the backup and replication operations. If necessary, the user can
use the DR repository as a backup target. The user must enter the DR mode at the DR
repository to start working with the DR site as their primary site.
21.2.1 Entering ProtecTIER DR mode
Keep the process for entering DR mode simple to avoid potential complications and human
errors when handling an emergency situation. The special DR wizard in ProtecTIER Manager
at the DR site facilitates the initiation of DR mode. DR mode blocks all replication activities
(including visibility switch) at the DR site from the failed primary site (and at that primary site if
it is still up).
Network failure: If a network failure occurs during replication, the system tries, up to
seven consecutive days, to replicate any specific cartridge that did not finish its replication
because of the line failure.
336 IBM ProtecTIER Implementation and Best Practices Guide
Figure 21-1 shows an example of entering ProtecTIER DR mode.
Figure 21-1 Entering ProtecTIER DR mode
As shown in Figure 21-1, you complete the following steps to entering the mode:
1. From the Systems Management view, click the destination repository.
2. Click Replication Replication Disaster Recovery Enter DR Mode.
3. Choose the repository you want to enter DR mode and confirm the selection.
An automatic procedure is run that blocks incoming replication to the DR site from the
source selected.
21.2.2 Working at the disaster recovery site
Replicated cartridges at the DR (hub) repository that are created at a primary site (spoke) are
in read-only mode. If it is necessary to run local backups at the DR site, and use new, locally
created cartridges.
Failback is the procedure for replicating back updated cartridges, new or old, from the DR site
to the original (or restored) production site to bring it up-to-date in case it was down, or lost
and rebuilt. You use failback to return to the original working mode of the primary site.
Important: Entering and activating ProtecTIER DR mode allows you to have all tape
cartridges with the latest data visible at the remote site with read/write access. However,
the backup application must be restored manually or by using prepared semi-automatic
procedures and scripts. You must be familiar with this backup application
recovery process.
Failback: The failback procedure can be initiated only in DR mode. It is mandatory to
perform the failback process before leaving DR mode at the remote disaster site.

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