Average File Size; File System Type - HP BL536A User's & Service Manual

To find the performance bottlenecks in your system, check the specifications and performance of
the:
Average file size (page 96)
File system type (page 96)
Connection from the host server to the disks (page 97)
Operating system configuration (page 100)
Backup server (page 101)
Backup type (page 101)
Connection from the host server to the device (page 102)
Media (page 103)

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 27 Performance impact of various file sizes
Average file size
<64 k: small files
64 k – 1 mb: medium
files
>1 mb: large files
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
96 Troubleshooting
Performance impact
POOR. Lots of small files require the disk to
perform many random accesses instead of a
continuous read.
NEUTRAL. Performance accessing
medium-sized files should be okay. The disks
will still need to do a fair number of random
accesses.
GOOD. Large files let the disk do less seeking
and spend more time doing continuous reads.
None. File size is irrelevant for Image or
sequential backups.
Table 27 (page 96).
Recommendations
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
backup, could offer some performance gains.
See above for drawbacks.
None.
None.
Table 28 (page 97)