Tape capacity

Technically, NBU knows nothing about tape capaicty - the density, hcart, hcart2 etc ... have no technical meaning, they are just a label.

It would be better to replace the densities with colours, green, red, blue - a green tape will ONLY go into a green drive and so on.  For example, I have a 4mm drive on one server, I can call that hcart3 and the tapes hcart3 , it will work fine, but the capacity of the tape remains the same.

THE EOT marker mentioned by JH is detected by the tapedrvie firmware, not directly by NBU.

Aside of not understanding tape capacity, NBU  does NOT actually write data to tapes directly.  It passes the data to the operating system, and requests it is written to tape using block size x.  NetBackup then relies on the operating system to complete the task.  This is the reason that in more cases than not, tape drive issues are not the fault of NetBackup.

The data is sent from NetBackup to the operating system, a block at a time - at some point the EOT marker is detected by the tape drive - there is sufficient physical tape left to finish writing that block, but at this point, the firmware causes a 'tape full' flag to be set in the tape driver.

NetBackup then sends the next block of data, at this time, the tape driver (via the os) refuses the data, and a 'tape full' message is passed back to NetBackup.  At this time, a new tape is loaded.

Regards,

Martin