Optimizing Performance - HP VS160 - StorageWorks DLT Tape Drive Troubleshooting Manual

Optimizing performance

We strongly recommend that you check the information on our web site at www.hp.com/
support/pat. This contains detailed support information that will enable you to identify
bottlenecks and take full advantage of the performance capabilities of the DLT VS160 tape
drive.
Various factors can affect tape drive performance, particularly in a network environment or if
the drive is not on a dedicated SCSI bus. If your tape drive is not performing as well as
expected—for example, if backup windows are longer than expected—consider the following
points before contacting HP Support at
Is the tape drive on a dedicated SCSI bus?
For optimum performance, we recommend that the tape drive is the only device on the SCSI
bus. If it is not, ensure other devices are LVD-compliant. If they are single-ended, the bus will
switch to single-ended mode with a lower transfer speed. There will also be restrictions on
cable length.
Can your system deliver the required performance?
The HP StorageWorks VS160 tape drive can write uncompressed data at up to 8 MB/s (28.8
GB/hour) or compressed data at up to 16 MB/s (57.6 GB/hour), assuming 2:1 compression.
However, to get this performance it is essential that your whole system can deliver this
performance. In most cases, the backup application will provide details of the average time
taken at the end of the backup.
Typical areas where bottlenecks can occur are:
• Disk subsystem
A single spindle disk may not be able to deliver good data throughput at poor compression
ratios. Best practice to ensure good throughput is to utilize multiple disk spindles or data
sources.
• System architecture
Be aware of the architecture of your data protection environment; the aggregation of
multiple client sources over a network provides a good way of delivering good performance,
but anything less than Gigabit Ethernet may limit performance. Some enterprise class
backup applications can be made to interleave data from multiple sources, such as clients
or disks, to keep the tape drive working at optimum performance.
• Tape media type
The data cartridge should match the specification of the tape drive. A lower specification
will have a lower transfer speed (see "Data cartridges" on page 23). Use DLT VS1 160 GB
cartridges.
www.hp.com/support .
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