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Why virtualized tape?

Sep 09, 20033 mins
Backup and RecoveryData Center

* Virtualized tape is a disk that looks like tape

Tape has never been a particularly popular format for doing backups.  When I started dealing with tape in 1981 it was slower than molasses, but then so was everything.  Today, in most cases it is faster than most molasses but still slower than disk, and with its penchant for requiring restarts at the worst possible moment during a backup, it often seems to be finicky.  Every one of us has had bad experiences with tape, and as a result every one of us has something bad to say about tape, tape drives, and the people who love them.  In fact, about the only thing tape has going for it is that, when all is said and done, it still works just fine in almost all circumstances.

I suppose this is a good time to admit that despite all this, there is still a fair-sized group (perhaps a million IT managers?) whose feelings about tape are reminiscent of the bumper sticker that says: “YOU CAN TAKE IT AWAY FROM ME WHEN YOU PRY IT FROM MY COLD, DEAD FINGERS!”

Feelings about tape often run high, so it is no wonder that figures like National Tape Association (NTA) president Charleston Harlston have been known to go before Congressional committees, wave a tape cartridge over their heads, and sternly proclaim that “Tape media doesn’t kill recoveries, managers with tape media kill recoveries!” Or words to that effect.

I wonder what all these folks on both sides of the issue think about virtual tape libraries (VTL)?

A VTL tries to offer the IT shop the best of both tape and disk storage.  Any operating system that sees one of these devices thinks it is a tape drive, and manipulates it as such.  The operating system saves to it and recovers from it as if it were tape, and back-up and recovery software do the same.  But it is not tape; it is disk that looks like tape.

Why would anybody want such a thing?  Lots of reasons. First, because it is disk-based technology, it is inherently faster than tape.  So anyone with fears about not finishing backups within the maintenance window has a reason to like it.  Second, any manager with a heavy investment in backup and recovery software, which invariably means a significant investment in tape management  software, would be able to use the faster technology without changing existing procedures.

Additionally, because the back-up data can be moved at any time from the virtual tapes to the physical tape media (thus freeing up the virtual disks for the next round of backups), the VTL is ready to go again. 

As an alternative approach, sites paying attention to information lifecycle management (ILM) can back up their most valuable data to these devices, and always have an immediately available dataset for recoveries. 

As ILM continues to develop, I am willing to bet that VTLs – and the serial ATA (SATA) drives that populate them – will become a major contributor to that technology’s advance.