Hi Mark,
Can you confirm whether the following are defined on the media server?
SIZE_DATA_BUFFERS
NUMBER_DATA_BUFFERS
NET_BUFFER_SZ
...and if they are, then what the values are.
If they are not defined, then enable level 5 logging for bptm on the media server, and then run a test backup and then search the bptm logs for:
"data buffer size" tells you what your SIZE_DATA_BUFFERS is...
"data buffers" and "io_init:" tells you what your NUMBER_DATA_BUFFERS is...
"receive network buffer is" tells you what your NET_BUFFER_SZ is...
I know that LTO1 and LTO2 drives have a hardware 256KB buffer. NetBackup defaults to sending data to the tape drive in 64KB chunks to maintain default compatibility with older DLT tapes and older SCSI HBAs. I strongly suggest that you look at increasing your SIZE_DATA_BUFFERS to 256KB, i.e. 262144.
For modern installations I would also set the client communication send buffer size to 256KB, and also the media server receive buffer size (i.e. NET_BUFFER_SZ). This way, you would have 256KB buffers all the way from the client through the media server through to the tape drive.
The whole toipic is rather too much to repeat here, and many web pages etc refer to such things. I really recommend that you look for an article by George Winter, re NetBackup Performance Tuning:
http://eval.veritas.com/downloads/van/4019.pdf
As for my points above, they may be enough to help you. Other people/pages/blogs report a quadruple performance jump from 16MB/s (same as your speed) to 60MB/s+ when using the above.
You'll have to research what the best setting for NUMBER_DATA_BUFFERS is, as this eats memory. The memory consumption is calculated as:
mem used = (buffer_size * num_buffers) * drives * MPX
i.e:
MEM_USAGE = SIZE_DATA_BUFFERS * NUMBER_DATA_BUFFERS * DRIVES * MPX
The only time that you won't want to make any changes to buffering is if your DR site/machine will be using direct attached SCSI tape drives. All modern FC HBAs, switches and LTO tape drives work best with 256KB buffers - BUT you will *NOT* be able to read the tapes on some low-end SCSI HBAs on Windows (and maybe Unix too). (Actually you can, even the Adaptec 29160 can be made to read/write 256KB with a simple and supported registry change), but, as ever, backward compatibility demands that NetBackup ships with a default 64KB, and that this is actually a definite performance hindrance for mdern systems.
If your DR server is FC too, then you have no excuses for not using 256KB data buffers.
Here's an HP article talking about LTO3 drives and NetBackup...
http://h71028.www7.hp.com/ERC/downloads/5982-9971EN.pdf
Check from page 37 to 41.
As ever, always test backup and retore after making these changes. And test that you can restore from backups before the change - and always have a backout plan.
One last thing, make sure you haven't enabled compression on the policy. This is only useful in some DSU scenarios, and should never ever be enabled for writing to LTO tape drives, as all LTO drives implement hardware compression by default.
Regards,
Dave.