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Re: [ARSCLIST] Hard disk drives and DAT

I've been following this thread closely, and think a valuable 
exercise would be to create detailed cost models for different 
storage scenarios.  Scenarios might include:

   - Hard disk on a shelf
   - Optical media (gold CD-R, DVD-R, Blue Ray)
   - Managed storage (mirrored on-line storage, tape back-up)

Common to each storage scenario:

   - Model three different size collections (1 TB, 10 TB, 50 TB)
   - Model a 50-year or 100-year life cycle
   - Make reasonable assumptions for media checking, refreshing,
     migration, and physical storage
   - Make assumptions about density and technology evolution 
     (Moore's law-ish)

Maybe there are other storage scenarios to be considered, and 
other details to be considered, but you get the idea.  If I were
an IT expert, I'd crunch these cost models myself.

The ideal scenario will simply be the one with the lowest total
cost, since data integrity, migration, short-term and long-term 
costs will all be accounted for, and the end goal (reliable 
long-term storage of data) will be the same for each scenario.

I think all scenarios are viable - even the hard disk on the
shelf (so long as you have redundancy, check the integrity of
the drive and the data at some scheduled interval, and have a 
budget to deal with drive failure and data recovery as needed,
and refresh the hardware at some reasonable interval).

I expect that different storage scenarios will be appropriate for 
different collection sizes (1 vs 10 vs 50 TB).

To me, this seems like a pretty logical approach to the problem
of storage of digital assets for preservation.  As a collection
grows, different storage scenarios will make sense.  The question
for many is what storage scenario do you start with, and at what
point do you transition to the next level storage scenario.  In 
the end, it's all cost driven (again, we're assuming that we drive 
each scenario to equivalent levels of reliability through redundancy
or other means).

I'd be surprised that no one has ever thought of working through
these different scenarios with a detailed cost model in order to
determine storage strategy and policy at some institution.

It's not rocket science, and the answer should be fairly straight-
forward I would think once you've captured all the costs and 
reliability aspects (just because it's straight-forward doesn't
mean that it's easy!).

So, does anyone know of an existing cost-based study of long-term 
data storage for several different scenarios AND several different
size collections?  If not, I may need to sharpen my pencil...

Eric Jacobs

The Audio Archive
tel: 408.221.2128
fax: 408.549.9867

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