HP Ultrium 232e, Getting Started Manual

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32
Optimizing performance
Various factors can affect data throughput, 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 points in
this section before contacting HP Support at
www.hp.com/support
.
Is the tape drive on a dedicated SCSI bus?
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.
Auto termination powers down when the tape drive powers down. This can cause a problem,
if there are other devices on the SCSI bus.
Can your system deliver the required performance?
• The Ultrium 448 tape drive can write uncompressed data at up to 24 MB/s (86 GB/hour)
or compressed data at up to 48 MB/s (172 GB/hour), assuming 2:1 compression.
• The Ultrium 232 tape drive can write uncompressed data at up to 16 MB/s (59.6 GB/hour)
or compressed data at up to 32 MB/s (119.2 GB/hour), assuming 2:1 compression.
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 for Ultrium 448 tape drives.
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 Ultrium 400 GB
cartridges with Ultrium 448 tape drives and Ultrium 200 GB cartridges with Ultrium 232
tape drives.
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 Ultrium family of
tape drives.