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VTL and NAS – Data source performance bottleneck
identification
In a lot of cases backup and restore performance using the HP D2D Backup System is limited by factors outside
of the appliance itself. For example the speed at which data can be transferred to and from the source disk
system (the system being backed up), or the performance of the Ethernet or fibre channel SAN link from source to
D2D.
Performance tools
In order to locate the bottleneck in the system, HP provides some performance tools that are part of the Library
and Tape Tools package (downloadable free from http://www.hp.com/support/tapetools) or can be used in
standalone mode (downloadable free from http://www.hp.com/support/pat).
The tools are:
Dev Perf – This provides a simple test that will write data directly from system memory to a cartridge in a library
on the D2D system. If this tool is run on a server being used as the backup media server it can provide the
maximum data throughput rate for a single backup or restore process. This will help to identify whether the D2D
system or data transport link (Ethernet or FC SAN) to the D2D system is the bottleneck because it isolates any
backup application or source disk system from the environment.
Running multiple instances of the Dev perf tool simultaneously to separate tape devices on the D2D will
demonstrate the performance that can be achieved with multiple backup streams.
Sys Perf – This tool provides two tests that are conducted on the source disk system to perform backup and
restore performance tests. These tests either read from (for backup) or write to (for restore) the system disks in
order to calculate how fast data can be transferred from disk and, therefore, whether this is a bottleneck.
These tests should be run on the media server that backs up to the D2D. In order to test how fast any client
servers can transfer data, the same performance tests can be used by mounting a directory from any of the client
servers to the media server then running the test from the media server against these mounted directories. This will
show how quickly data can be transferred from the client server disk right through to the media server.
For example if the source data can only be supplied at 20 MB/sec – the D2D cannot backup at any faster than
20 MB/sec!
Performance metrics on the Web Management Interface
D2D appliances with software at version 1.0.0 and 2.0.0 and later will also provide some performance metrics
on the Web Management Interface.
For backups, restores and replication for both VTL and NAS modes the current transfer rate and 5 minute history
is displayed graphically in the activity monitor, see examples on the next two pages. For replication examples
see Replication Monitoring on page 67. This display can be used in conjunction with the LTT tools to help
identify performance bottlenecks and aid the user when tuning the appliance for best practices.