[Beowulf] Big storage

Robert G. Brown rgb at phy.duke.edu
Thu Aug 30 15:03:55 EDT 2007


On Thu, 30 Aug 2007, Leif Nixon wrote:

> "Robert G. Brown" <rgb at phy.duke.edu> writes:
>
>> On Thu, 30 Aug 2007, Jakob Oestergaard wrote:
>>
>>> I find it interesting (and surprising) how little people like tape :)
>>
>> It isn't that difficult to understand.  People WOULD like tape and USED
>> to like tape back when a single tape on a single tape drive would back
>> up your whole system.  I even remember those days.  But what, maybe
>> seven or eight years ago the hard disk curve (which has an even shorter
>> capacity doubling time than Moore's Law does for the rest of the system)
>> crossed over the tape curve (which has a MUCH longer one) and life has
>> sucked ever since.  Tape backups even back when they still "worked",
>> kind of, had gotten madly expensive compared to the disk they were
>> backing up -- you could pay $1000 for disk and $3000 for the tape backup
>> unit really easily.
>
> But now you're talking backups. That's not quite the same thing as
> having an HSM system where the bulk of the data is stored on tape and
> (supposedly) transparently migrated from and to front-end disk caches.

Absolutely.  We had to look over a lot of that sort of thing when we
were making an ATLAS proposal.  But again, IMO all the solutions for
that sort of thing are tough ones and expensive ones.  There is plenty
of data on the web about the unreliability of tape -- on sites that
really use tape as primary backup and that have the usual multiple disk
crashes a year that they have to restore from tape, failure rates are
something like 40% -- one restore failure every two, two and half years.

    rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu


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