Testing Tape Drive Speed

To determine the best configuration of your tape drive, you can run the speed command available in the btape program.

This command can have the following arguments:

file_size=n: Specify the Maximum File Size for this test (between 1 and 5GB). This counter is in GB.
nb_file=n: Specify the number of file to be written. The amount of data should be greater than your memory (file_size * nb_file).
skip_zero: This flag permits to skip tests with constant data.
skip_random: This flag permits to skip tests with random data.
skip_raw: This flag permits to skip tests with raw access.
skip_block: This flag permits to skip tests with Bacula block access.

*speed file_size=3 skip_raw
btape.c:1078 Test with zero data and bacula block structure.
btape.c:956 Begin writing 3 files of 3.221 GB with blocks of 129024 bytes.
++++++++++++++++++++++++++++++++++++++++++
btape.c:604 Wrote 1 EOF to "Drive-0" (/dev/nst0)
btape.c:406 Volume bytes=3.221 GB. Write rate = 44.128 MB/s
...
btape.c:383 Total Volume bytes=9.664 GB. Total Write rate = 43.531 MB/s
btape.c:1090 Test with random data, should give the minimum throughput.
btape.c:956 Begin writing 3 files of 3.221 GB with blocks of 129024 bytes.
+++++++++++++++++++++++++++++++++++++++++++
btape.c:604 Wrote 1 EOF to "Drive-0" (/dev/nst0)
btape.c:406 Volume bytes=3.221 GB. Write rate = 7.271 MB/s
+++++++++++++++++++++++++++++++++++++++++++
...
btape.c:383 Total Volume bytes=9.664 GB. Total Write rate = 7.365 MB/s

When using compression, the random test will give your the minimum throughput of your drive. The test using constant string will give you the maximum speed of your hardware chain (cpu, memory, scsi card, cable, drive, tape).

You can change the block size in the Storage Daemon configuration file.