In bed with tape
- 01 March, 2006 09:52
"Just when I thought I was out, they pull me back in." -- Michael Corleone, The Godfather: Part III
This often-repeated quote comes to mind whenever I hear IT managers assert that "our goal is to get rid of tape." They probably have not fully investigated the issue or considered all of the factors necessary to truly eliminate tape from their environments.
While elminating tape is technically feasible, there are several roadblocks that will in all likelihood prevent this, all of them economic.
First is the calculated cost of enough disk storage to eliminate tape. Serial ATA disks are certainly cheap and getting cheaper, but backup data typically requires six to 10 times the storage of primary data. Can you afford to buy and operate -- meaning house, power, cool and manage -- this additional storage? By the way, don't forget to factor in data growth as well.
Next, unless you are seriously re-architecting your backup environment, the most likely approach to tape elimination is via a virtual tape library. This means an additional premium for the VTL functionality beyond simply the cost of a storage array. With or without a VTL, there may also be additional software licensing fees to integrate or effectively leverage the disk-based system with your backup software.
Finally, there is the issue of off-site data. You will never get rid of tape unless you are replicating all your data in some way, shape or form to a disaster recovery site. Don't forget about archival data, too.
Therefore, the reality for most is that disk-based backup can dramatically improve data protection services -- speeding backups, reducing failures, improving recoverability -- and can reduce but not do away with reliance on tape. Just eliminating tape as a performance bottleneck or problem source in the nightly backup process can be a huge win.
For those truly committed to the no-tapes vision, don't despair. I would suggest considering products that incorporate aggressive data-reduction technologies, such as delta-block differencing or commonality factoring, which can store backup data in a fraction of what would otherwise be required. Companies like Avamar Technologies, ExaGrid, Data Domain and others are pioneering the use of these and other technologies to make disk-only backup feasible.
Jim Damoulakis is chief technology officer of GlassHouse Technologies, a leading provider of independent storage services. He can be reached at firstname.lastname@example.org.