The answer to the question is only when the tape drive cleaning light is on
Yesterday I was having a discussion with a frontline engineer about cleaning tape drives.
Apparently a customer had had several replacements of their DLT tape drive
and wanted to know what proactive measures they could take to avoid needing to replace their drive in the future.
So I had a look at the messages which they had used to justify replacement, and in each case the sense key was "media error." This set alarm bells ringing, because if a DLT
drive reckons there is a problem with the media then you either have a problem with that tape, or an environmental problem which makes the tape media a carrier (like a bacterium in a way).
The technology and intelligence which is designed into the DLT and LTO families is such that you should never need to use a cleaning tape. And if you do, it is only because the drive itself has detected that it needs a clean.
I remember a performance escalation a few years back where it turned out that the customer was running cleaning tapes through their DLT drives twice a week. This was completely unnecessary and had the decidedly unwanted effect of killing the drive's read and write performance as the heads were degraded. Replacing the drives was their only option.
Other customers have configured frequency-based cleaning in NetBackup
or Solaris Backup
/ Legato Networker
--- this is a complete nono. Use the TapeAlert
function of the drive and configure cleaning for "on-demand" only.
If you keep your DLT and LTO drives in a minimally-dusty environment and don't throw your tapes around you should never need to use a cleaning tape.