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Resumen del manual
Data Backup
Automatic normalization is a benefit of using the remote copy set function of DRM. If an operations
manager wants to make a copy of a unit for archival or backup, a simple backup method would be to
replace the target copy with a “new” logical unit number (LUN). This makes the backup copy
immediately available, and normalization creates another copy at the target site. Refer to “Data Backup
by Disk Rotation” on page 17 for this backup procedure. If the operations manager is not comfortable
with having the disaster-tolerant configuration in a regular normalization, then the operations manager
can simply create a clone copy.
Disk Vaulting
Each time a disk-to-disk clone is made, the cloned copy can be removed from a cabinet without having
to shut down the controller or stop other operations. You would rotate the disks in a vault just like you
would rotate tapes. When vaulted disks become obsolete, they are placed back into the cabinet for
future cloning.
For example, you decide that a full copy is to be made of a specific volume each day. The vault
contains the “yesterday” volume and the “day before” volume. When the “today” cloned volume is
created, it is placed in the vault and the “day before” volume is placed back into the same cabinet slots
that the “today” disks used. The order of the disks in the slots is not important. EVM then runs the
UNDO CLONE utility and the “day before” disks are added back into the three-member mirrorset or
striped mirrorset. Data is completely rewritten to the replacement member as part of the normalization
process. The volume becomes tomorrow’s “today” volume. This process can be repeated on any
schedule that meets the user’s requirements.
Disk-to-Tape Backup
Using DRM with EVM, the time to back up to tape drives becomes less of an issue. Tape backup can
still be used with large amounts of data that is offline to the application server, causing little impact on
normal operations.
If you wish to back up volumes to tape, EVM runs the cloning process on any unit at the target site,
creates a unit for the clone, and mounts it to a backup server. Again, using three-member mirrorsets or
striped mirrorsets reduces the cloning time to a few seconds instead of hours.
The tape backup utility can start EVM, or EVM can start the tape backup utility. Either way, EVM can
selectively make clones of JBODs, mirrorsets, stripesets, or mirrored stripesets. In cases where disks
are at a premium, you may want to use RAID 3/5 sets. These provide excellent data protection while
using a minimum number of disks (N+1). Cloning is not possible on RAID 3/5 sets, but an alternative
method called a snapshot can be used.
A snapshot is an instantaneous logical copy that can be mounted to a host. This makes snapshots
desirable in a tape backup solution because they can be created quickly. Although a physical device is
used, the data mostly remains on the original or source LUN. Snapshots may be created only on the
target site and are not removable (see Figure 4). Information on manually creating clones and
snapshots is available in the Data Replication Manager HSG80 ACS Version 8.6-1P Configuration
Guide as an appendix titled “Replicating Storage Units.”
Compaq has also developed a tool called Enterprise Backup Solutions (EBS) to support the
management of tape backups. It provides tape hardware (drives, robots, and fiber translators)
compatible with a number of third-party backup software (for example, Veritas Backup Exec and
Netbackup, Computer Associates ARCserv and Legato-Networker, and IBM Tivoli). A simplified
logical configuration that shows how EBS may be used is illustrated in Figure 5. Tape backups are
performed on the target site and only non-DRM volumes are backed up at the initiator site.
Application Notes - Maximizing Efficiency Through Data Replication Manager Data Movement
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