HP StoreEver MSL2024, MSL4048, MSL8048, and MSL8096 Tape Libraries User and Service Guide (AK378-96059, December 2012)

To find the performance bottlenecks in your system, check the specifications and performance of
the:
• “Average file size” (page 154)
• “File system type” (page 154)
• “Connection from the host server to the disks” (page 155)
• “Operating system configuration” (page 155)
• “Backup server” (page 156)
• “Backup type” (page 157)
• “Connection from the host server to the device” (page 158)
• “Media” (page 159)
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 35 (page 154).
Table 35 Performance impact of various file sizes
RecommendationsPerformance impactAverage file size
POOR. Lots of small files require the disk to
perform many random accesses instead of a
continuous read.
<64 k: small files
• If possible, do NOT use a file-by-file
backup method.
• For backups with an average file size <64
k, HP recommends using a
sequential/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.
No change is necessary but using a
sequential backup method, such as an image
NEUTRAL. Performance accessing
medium-sized files should be okay. The disks
64 k – 1 mb: medium
files
backup, could offer some performance gains.
See above for drawbacks.
will still need to do a fair number of random
accesses.
None.GOOD. Large files let the disk do less seeking
and spend more time doing continuous reads.
>1 mb: large files
None.None. File size is irrelevant for Image or
sequential backups.
Image or sequential
backup
File system type
The file system determines the organization of the files on the disks. When the files are spread
over multiple disks with multiple controllers, some disks can be seeking while others are reading.
Find the performance impact of your system's file system in Table 36 (page 155)
154 Troubleshooting