[Beowulf] PetaBytes on a budget, take 2

[David Mathog]

Joe Landman wrote:

> My biggest argument against tape is, that, while the tapes themselves 
> may last 20 years or so ... the drives don't.  I've had numerous direct 
> experiences with drive failures that wound up resulting in inaccessible 
> data.  I fail to see how the longevity of the media matters in this 
> case, if you can't read it, or cannot get replacement drives to read it. 
>   Yeah, that happened.

20 years is a long, long time for digital storage media.  

I expect that if one did have a collection of 20 year old backup disk
drives it would be reasonably challenging to find a working computer
with a compatible interface to plug them into.  And that assumes that
those very old drives still work.  For all I know there are disk drive
models whose spindle permanently freezes in place if it isn't used for
15 years - it's not like the drive manufacturers actually test store
drives that long.  While it is unquestionably true that a 20 year old
tape drive is prone to mechanical failure, it would still be easier to
find another drive of the same type to read the tape then it would be to
repair the equivalent mechanical failure in the storage medium itself
(ie, in a failed disk drive.)  That is, the tape itself is not prone to
storage related mechanical failure.

All of which is a bit of a straw man.  The best way to maintain archival
data over long periods of time is to periodically migrate it to newer
storage technology, and in between migrations, to test read the archives
periodically so as to detect unforeseen longevity issues early, while
there is still a chance to recover the data. 

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech