How to achieve over 2 TB/hr network backup with Integrity entry-class servers running HP-UX 11i v3

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o One set of restores left the client file data in place and used the “No overwrite” option of
Data Protector for the data restore operation (referred to hereafter as a “No Overwrite
Restore”). A “No Overwrite Restore” restores only the missing files in a file system and
retains existing files. With the “No Overwrite Restore” operation, Data Protector simply
reads data from tape on the backup server and transmits the data over the network to the
client; because the files already exist on the client system, they are not written to the client’s
file system and disk. This confines measurement of the restore performance to the tape
devices and the network infrastructure only, eliminating the effect of file system, data write
latencies, and disk bandwidth limitations.
o Another set of restores was performed after deleting from the client file systems all the data
files that were backed up. The restores were run using the default options of Data Protector.
Because previously backed-up data no longer exists in the client system’s file system, all data
in the backup is restored (hereafter referred to as a “Cold Restore” operation). The “Cold
Restore” operation reads from tape and transmits backup data from the backup server to the
client, taking additional time to allocate the “new” files in the client file system, to allocate file
extents, and to write all the file data to the client’s storage.
Note
The overall restore performance of the client file systems could likely be improved with specific
tuning on the client systems; however, the objective of this particular network backup
characterization was to leave tuning optimal for the applications and services that are the primary
function of the client system.
Figure 7 shows the results comparing backup and restore performance using the rx3600 backup
server. The data backup and the two restore operations mentioned previously (“No Overwrite
Restore” and “Cold Restore”) were each tested with an increasing number of tape devices (from one
to four).
Figure 7: Comparing backup and restore performance using an rx3600 server
The “No Overwrite Restore” operation (which excludes actual writing of restore data to the file system
and disk) scales well, averaging two-thirds of the backup throughput performance. The results of the
“Cold Restore” operations show the effect that writing data to the file system and disk has on the
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1 Tape
2 Tapes
3 Tapes
4 Tapes
Total Data Throughput (MB/s)
Backup
"No Overwrite Restore"
"Cold Restore"