Archive for November 28th, 2002
What a week, starting with the Enterprise Backup Solutions (EBS) training course I give. As before, the biggest problem is actually getting hardware for the students to use to build a backup solution. It calls for one setup per three people, and a typical EBS setup includes a server with Fibre Channel adaptors, a SAN Switch, a “Data Router” that translates data and commands between Fibre Channel and different SCSI cabling types (depending on what cards you have plugged in).
Then there’s the “library”, which in generic terms is a bunch of tape drives inside a housing with tape storage slots and one or more “robot” mechanisms that shift tapes around between slots and drives. A library robot operates in almost the way you imagine, looking and sounding like something from Blue Peter or the Discovery Channel.
Libraries vary in size, from a rack-mounted box 2U (3.5 inches) in height, to a free-standing cabinet that takes up half the room, with a capacity measured in tens of terabytes. In the latter case the robot will not work if the door is open, for safety reasons. (It could rip your arm off at the shoulder.) A library is a pretty dumb system, and it relies on software running on the server to control the robot(s) and manage the tapes.
The robot part of the system doesn’t go wrong much, but we have far more problems with the SCSI communications side, with each 68-pin cable practically a fault waiting to happen. It’s a prime candidate for replacement with new technologies such as Serial Attached SCSI (SAS), which has the potential to be more reliable.
This is a field I need to keep one eye on, and writing a little piece like this helps me get my thoughts in order. In case you’re wondering why I’m doing this…