HP StorageWorks User Manual page 59

The Ultrium 448 tape drive can write uncompressed data at up to 24 MB/s (86 GB/hour).
To obtain this performance it is essential that your whole system can deliver this performance. In most
cases, the backup application will provide details of the average time taken at the end of the backup.
Typical areas where bottlenecks can occur are:
Disk subsystem
A single spindle disk may not be able to deliver good data throughput at poor compression ratios.
Best practice to ensure good throughput is to utilize multiple disk spindles or data sources.
System architecture
Be aware of the architecture of your data protection environment.
The aggregation of multiple client sources over a network provides a good way of delivering good
performance, but anything less than Gigabit Ethernet will limit performance for Ultrium tape drives.
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.
Tape media type
The data cartridge should match the specification of the tape drive. A lower specification will have
a lower transfer speed (see
Ultrium 3 TB R/W or Ultrium 3 TB WORM cartridges with Ultrium 3000 tape drives
Ultrium 1.6 TB R/W or Ultrium 1.6 TB WORM cartridges with Ultrium 1760 tape drives
Ultrium 800 GB R/W or Ultrium 800 GB WORM cartridges with Ultrium 920 tape drives
Ultrium 400 GB R/W cartridges with Ultrium 448 tape drives
Data and file types
The type of data being backed up or restored can affect performance. Typically, small files incur
greater overhead in processing and access than large files. Equally, data that is not compressible
will always limit the speed at which the drive can write/read data. You will achieve no more than
native rates with uncompressible data.
Examples of files that compress well are plain text files, spreadsheets; those that compress poorly
are those that are either compressed as part of their format (such as, JPEG photographic files) or
stored as compressed (such as, .ZIP files or .gz/.Z files on UNIX platforms).
"Data cartridges" on page 47). Use:
Ultrium Half-Height SAS Tape Drives 59