Veritas-bu

[Veritas-bu] Tape Media Advise

2001-07-25 13:50:19
Subject: [Veritas-bu] Tape Media Advise
From: John_Wang AT enron DOT net (John_Wang AT enron DOT net)
Date: Wed, 25 Jul 2001 12:50:19 -0500
Hello Elmer

Realistically, if the tape holds incremental or differential backups then it
will conceivably have hundreds of mounts before one full pass of the tape is
achieved.   I believe that my AIT2 tapes will typically get mounted 200 times
before they are considered full.   You can fill the tapes faster by increasing
the MPX on the tapes and decrease the number of tape drives used but that is at
the expense of speed of backups overall.   I would've far preferred the metric
of full passes to mounts to age out tapes, I think that back in the old days of
9 track reel to reel tapes, HP recommended no more than 5 overwrites hence five
full passes, of course no one respected that and reused tapes till they dropped.
I suppose that you could take a look at the number of images on an existing full
tape, multiply that by 5 and use that as your maximum mount count but even then
it would not be accurate as full backups would use far more tape per mount hence
you would need to set their mount counts separately.

I'm taking the reuse them till they drop attitude.   If a single tape flags
errors on multiple drives as reported in the media log report than I freeze the
tape, make note of it in my notes and when it expires, I degauss and toss the
tape (I also delete altogether from the media manager).   I'll be damned if a
silly $100 tape gives me any grief.

Regards,
John I Wang
Sr. Systems Engineer
Steverson Information Professionals

---
Enron Networks
Enron Building room 3427e
ph (713) 345-4888
cell (832) 493-1263
fax (713) 646-8462
pg pagejwang AT skytel DOT com or 1-877-390-4155





|--------+----------------------->
|        |          Elmer.bantay@|
|        |          sscims.com   |
|        |                       |
|        |          07/25/01     |
|        |          12:16 PM     |
|        |                       |
|--------+----------------------->
  >--------------------------------------------------------------------|
  |                                                                    |
  |       To:     veritas-bu AT mailman.eng.auburn DOT edu                    |
  |       cc:     (bcc: John Wang/Contractor/Enron Communications)     |
  |       Subject:     [Veritas-bu] Tape Media Advise                  |
  >--------------------------------------------------------------------|



Hello All,

Need your advice on tape media maximum mounts.  What would be a good
recommendation for a maximum mounts for DLT IV (tape media)?  We had it
at 100 mounts (per tape) and now, we brought it up to 300 mounts.  I'm
just worried about the data being backed up if it exceeds 100 mounts on
a tape.  Please advice.

Thanks,

Elmer
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