Further to this, once the speed has been deduced you need to ensure you are running at a optimum speed. LTO2 drives should be able to write someware around 30MB/sec - so if your only getting 10MB/sec (sustained) then something is up.
For a given amount of tape there will always by the same amount of data stored, therefore if you feed the data out to the tapes to slowly (eg. bottlenect someware on system) the drives have to keep stopping, rewinding a bit then starting off again, known as 'showshining' it wears drives out quicker.
On the other extream, if you try and feed to much data, savesets end up being queued and your backup takes longer.
It is a balance between server parallelism and no of target sessions on drives.
Server parallelism - no of savegroups being streamed out, default is four. Target sessions is the no of sessions Networker should send to the drive, so a Parallism of 4 and target sessions set to 2 would mean that 2 drives would be required, or if one drive was available only, it would take approx twice as long to run the backup as if two drives were available. Setting the target sessions to 4 would allow all the streams to be written at once, therefore making more efficient use of the drive. Unfortunately, this is trial and error.
Martin
