[H-GEN] Tape Drives

Greg Black gjb at gbch.net
Thu Jan 10 02:35:31 EST 2002


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(I sent this message out yesterday but have not seen it.
Apologies to anybody who gets to see it twice.)

Jason Henry Parker wrote:

| Bruce Campbell <bc at humbug.org.au> writes:
| 
| > Decide whether you want speed, long-term reliability or small tape usage.
| > Two of these at the same time is usually not attainable ;)

Actually, I think you can have the first and third of these
together; I doubt if "long-term reliability" and "tape" belong
in the same sentence.

| Long-term reliability is a bit of a worry, though.  How would I
| reasonably go about testing it?  While I've never had a tape fail:

Seriously, for long-term storage, spinning disks are the best
bet.  Tapes are good for disaster recovery, but not for archival
purposes -- just storing tapes for some time can result in bits
falling off the media.

I have some rules with tape.  When I open a box of tapes, I
label each of the tapes with a batch number.  When I get a
single error from a tape, I destroy all the tapes in that batch
(after restoring or replacing any data they are holding).  I
maintain a label at the start of each tape which records a count
of uses and I throw the tapes away after a predetermined number
which varies according the tape type (50 for DDS-3).  I also
destroy tapes once 3 years has passed since they were first
written to.

|  (a) I've not had much call to use them, and getting enough time to
|      run verifies every day is a bit much.  I suppose I could test one
|      tape per slightly-less-than-the-dumpcycle.

You need to verify them often enough to know that they are OK or
else your whole disaster recovery plan can turn to dust.  I
don't do full restores for this -- I note which file gets dumped
last and restore that.  It's not foolproof, but it's good enough
for my purposes as I always have several copies of all important
data.

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