HP A7518B HP StorageWorks SDLT Tape Drive Getting Started Guide - internal mod - Page 38

Optimizing performance, Is the tape drive on a dedicated SCSI bus? - tape write speed

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Page 38 highlights

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 before contacting HP Support at www.hp.com/ support. 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 SDLT 600 tape drive can write data at 36 MB/s (native) or 72 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 a transfer rate of 72 MB/s). • 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 we strongly recommend 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. Performance checklist The following list summarizes factors that can affect performance. They provide a guideline only of areas that may need further investigation. They do not attempt to explain how to configure individual systems. For a more detailed discussion, including information about tools that allow you to test performance, refer to our white papers on www.hp.com. (Select the product first and look at the Information Library.) • Is the tape drive reading and writing data at the correct speed? • Is the source system (hard disk) transferring data at the correct speed? • Is the backup application writing buffers at the correct speed? You may need to tune the transfer, buffer and block size settings to optimize the speed that the application writes data to the tape drive. HP StorageWorks SDLT 600 tape drives have an internal buffer of 64 MB. 34

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34
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 before contacting HP Support at
www.hp.com/
support
.
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 SDLT 600 tape drive can write data at 36 MB/s (native) or 72 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 a transfer rate of 72 MB/s).
•
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 we strongly recommend 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.
Performance checklist
The following list summarizes factors that can affect performance. They provide a guideline
only of areas that may need further investigation. They do not attempt to explain how to
configure individual systems. For a more detailed discussion, including information about tools
that allow you to test performance, refer to our white papers on
www.hp.com
. (Select the
product first and look at the Information Library.)
•
Is the tape drive reading and writing data at the correct speed?
•
Is the source system (hard disk) transferring data at the correct speed?
•
Is the backup application writing buffers at the correct speed? You may need to tune the
transfer, buffer and block size settings to optimize the speed that the application writes data
to the tape drive. HP StorageWorks SDLT 600 tape drives have an internal buffer of 64 MB.