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Optimizing performance
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, consider the following points.
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.
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 460 tape drive can write data at 30 MB/s (native) or 60 MB/s (compressed -
assuming 2:1 compression), however, to get this performance it is essential that your whole
system can deliver this performance.
Typical areas where bottlenecks can occur are:
• Disk system (a single hard disk drive will not be able to deliver 60 MB/s transfer rates).
• Some file systems are able to transfer data faster than others.
• The type of data being backed up can affect backup performance (for example, file sizes
and compressibility).
• Some backup software performs better than others.
To improve performance you may like to consider a RAIDed disk solution with a large number
of physical hard disks.
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.
Is the data transfer rate too slow?
Adaptive Tape Speed (ATS) enables the drive to "stream" data at variable tape speed, which
means that it maintains a continuous data flow to tape even when the transfer speed varies.
This is automatically managed by the drive to keep the drive running at best performance.
When using Ultrium 2 cartridges, the ATS range is 10 -30 MB/s, so, if possible data transfer
should remain within this range. In most cases, the backup application will provide details of
the average time taken at the end of the backup.
Note For optimum performance always use Ultrium 2 400 GB cartridges. If you are using Ultrium 1
200 GB cartridges, the ATS range is 6.6-20 MB/s.
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