e i g h t - c u b e d . c o m 

DLT cleaning lights

Sorry about the lack of entries here lately. As usual, the day job has me fairly flat out.

After a number of years asking for a platform to develop a new backup solution on, we finally got our hands on a little AlphaServer DS25. The box has two CPUs and a gig of memory, and as it has fibrechannel adapters, we can attach it to a SAN to get access to lots of data to back up and tape drives to back up to.

One of the requirements for the new backup system was that it automatically detect when tape drives need cleaning. Currently, our operations staff manually load cleaning cartridges into drives as required, however, that's not very possible once backups commence.

A far better solution would be if the backup manager could detect that a drive needs cleaning and could automatically load a cleaning tape, even in between backing up individual disks.

Placing cleaning tapes in the silo is straight forward, but detecting when a drive needs cleaning was not so easy.

With DLT drives, it's possible to accomplish the magic by issuing a log sense SCSI command to read the tape alert page, which contains the bit to indicate the cleaning light is on.

When all is said and done, the code is reasonably simple (after I decoded the SCSI specification ;). After I clean up the code a bit, I will publish it here.