You can use the dd command as a quick
test to estimate the best possible results for data flow to disks.
The command is available for operating systems such as AIX® or Linux.
About this task
The dd command can be useful if you do
not have or do not want to install more powerful tools. To estimate
peak performance under ideal conditions, use the dd command
to time how long a write to a device takes. Then, time how long a
read from the device takes.
Procedure
To run a write test, issue the following command.
time dd if=/dev/zero of=/device_path/filename bs=262144 count=40960
where device_path is
the name of the file system that you want to test, and filename is
the name of a file.
Important: The filename file
must not exist in the file system. If the file does exist, the command
overwrites it with zeros.
The output of this command gives
you the time that is required to write a 10 GB file in 256 KB blocks.
To run a read test of the file that was written, issue
the following command.
time dd if=/device_path/filename of=/dev/null bs=262144 count=40960
When you evaluate the command results, keep in mind that if
you just ran the write test that the data might still be in the disk
cache. The time reported by the command for the read operation is
therefore less than what you can expect for typical Tivoli® Storage
Manager server operations.
For typical Tivoli Storage
Manager server
operations, data is not likely to be in the cache and is read from
the disk itself.