HP StorageWorks MSL2024, User'S And Service Manual

Page: 166 / 276

Performance problems
TIP:
For more performance troubleshooting information, see the Performance Troubleshooting Guide at
http://www.hp.com/support/pat .
The process of backing up files goes through many devices, from the files in the file system on the
disk, through the backup server, and out to the Library, all managed by software running on an
operating system. The backup process can only run as fast of the slowest link in this chain.
To find the performance bottlenecks in your system, check the specifications and performance of the:
• “ Average file size ” on page 166
• “ File system type ” on page 167
• “ Connection from the host server to the disks ” on page 168
• “ Operating system configuration ” on page 171
• “ Backup server ” on page 172
• “ Backup type ” on page 173
• “ Connection from the host server to the device ” on page 174
• “ Media ” on page 176
Average file size
The hard drive must seek to the position of a file before it can start reading. The more time the disks
are seeking to files, the lower the performance.
To determine the average file size, divide the size of the backup by the number of files. See the
performance impact of your system's average file size in
Table 38 .
Table 38 Performance impact of various file sizes
Recommendations Performance impact Average file size
• If possible, do NOT use a file-by-file
backup method.
• For backups with an average file size
<64 k, HP recommends using a se-
quential/image backup that backs up
the hard drive or LUN image instead
of the individual files.
The drawback with the sequential/image
backup method is that you might only be
able to restore the entire disk image and
not individual files. If you can restore
individual files, the restore operation will
be very slow.
POOR . Lots of small files require the disk
to perform many random accesses instead
of a continuous read. <64 k: small files
No change is necessary but using a
sequential backup method, such as an
image backup, could offer some
performance gains. See above for
drawbacks.
NEUTRAL . Performance accessing
medium-sized files should be okay. The
disks will still need to do a fair number of
random accesses. 64 k – 1 mb: medium
files
Troubleshooting 166