Bryan Henderson wrote:
1) Tapeless: maintain multiple copies on disk (minimize
backup/restore lag)
Can you really call it archival if you're willing to pay 5 times as much
for quick access? Maybe you need a different word. Archive means large
quantities of data with very low access frequency. And sometimes, in the
current legal climate, with very low chance of destruction.
You word this as if the only potential use of tape is backup of disk-based
data, but it's also pretty useful as the primary copy of archival data.
I know some people swear by them, but our experience with tertiary (tape
and optical) storge systems has never been positive. (We have tried
several over the years, from several vendors.) Leave it at that, and
let's just say we want to explore new territory.
There is also an argument that the cost of tape and disk is slowly
converging/crossing. Some disagree, we find it an interesting point.
For many users, the cost of archival storage is often dominated by
non-hardware costs. Our internal departmental recharge rates for (tape)
backed-up storage are on the order of $5/month to $10/month per GIGABYTE
of storage. That's $60/GB/year to $120/GB/year. Very little of that
cost is hardware. Considering that a GB of disk now costs $1 to $2 for
commodity disks, I can afford to keep several copies of my data online
for quick access when I do want it, especially when it is mostly
archival and doesn't change that often (almost never).
Jeff Anderson-Lee
Petabyte Storage Infrastructure Project
University of California Berkeley
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