Disable Backup Application Verify Pass; Tape Copy Or Offload Performance - HP StorageWorks 12000 - Virtual Library System EVA Gateway Manual

servers. In this case, also ensure that bonded/trunk network ports are configured for both the
media server and the D2D device.
With either configuration there is a requirement to correctly configure the backup application to target
the devices correctly; this will usually involve creating multiple backup jobs to back up specific data
to selected virtual libraries.
Configuring backups to run in parallel rather than serially also improves replication and tape offload
operations because these run after backup jobs have completed. Having backups finish at roughly
similar times will ensure that the replication and tape offload jobs are not in contention with backup
jobs.
However, backup application vendors often base their licensing model on the number of tape devices
configured, so you may need to balance between performance and cost. Some applications (e.g.,
HP DataProtector) offer capacity based licensing (per TB) for virtual tape appliances; this licensing
model may be more cost effective because it allows you to configure any number of libraries or tape
devices.

Disable Backup Application Verify Pass

Most backup applications will default to performing a verify operation after a backup job. While this
offers a very good way to ensure that data is backed up successfully, it will also heavily impact the
performance of the whole backup job. Performing a verify operation will more than double the overall
backup time due to the fact that restore performance (required for verify) is slower for deduplication
enabled devices.
Disabling verify for selected backup jobs can be done relatively safely because D2D Backup Systems
perform CRC (Cyclic Redundancy Check) checking for every backed up chunk to ensure that no errors
are introduced by the D2D Backup System. However, if data is incorrectly written by the backup
application but is not corrupt, this will not be detected by the D2D. For this reason, verifying some
backup jobs is still recommended.

Tape Copy or Offload Performance

Copies of cartridges to physical media using the HP D2D Backup System can be achieved by using
either a directly attached tape drive or library where the offload is controlled by a manual or scheduled
operation from the D2D Web Management Interface, or by using a backup application on the media
server to copy data from a cartridge on the HP D2D Backup System to a tape device or library
connected to the media server. In either case, take the deduplication process into consideration when
scheduling the offload.
The D2D allows a tape offload to be automatically scheduled to start immediately after a backup to
the virtual tape completes; most backup applications provide a similar configuration option if performing
a backup application copy. Take care when using these options because they can result in slower
than expected offload performance due to some level of housekeeping running; also, if replication is
configured the two operations will clash and result in a delay to replication.
You should delay any tape offload for several hours after the backup completes if the backup is doing
a significant amount of data overwrite. Otherwise, the housekeeping process will have a detrimental
effect on the tape offload performance. As a general rule, for every 100 GB of data on the cartridge
being overwritten, allow 30 minutes to pass before starting an offload operation. Because it depends
on the deduplication ratio and amount of unique chunks contained in that backup, it is hard to
determine how many housekeeping operations will be generated (and therefore how long it will take
to run) by an overwrite backup.
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