Veritas-bu

[Veritas-bu] Fwd: Frozen Tapes

2009-09-03 11:25:05
Subject: [Veritas-bu] Fwd: Frozen Tapes
From: Dean <dean.deano AT gmail DOT com>
To: Veritas-bu AT mailman.eng.auburn DOT edu
Date: Fri, 4 Sep 2009 01:21:53 +1000
Yes, in my experience, a frozen tape is very rarely due to an actual I/O error writing data to the tape. It's usually due to robotic inventory inconsistencies, write protect, or something similar which really has nothing to do with the integrity of the tape itself.

And yes, even if you do get real I/O errors writing to a tape, it doesn't mean all of the data already written to the tape is unrecoverable. If there is one bad bit on the tape, all the other fragments that don't cross the bad part of the tape should still be completely fine to use for recovery.

As others have said, look through the logs for the actual error that is being thrown.

Cheers,
Dean


On Fri, Sep 4, 2009 at 12:26 AM, <judy_hinchcliffe AT administaff DOT com> wrote:
1)  if you have netbackup set up to overwrite a tape that has other
types of data on it, it will use it and not freeze it.  Depend on what
your settings are
2) yes it does not like to over write catalogs that is why your cat
tapes are in a different pool  and should always return to that pool so
you don't have this issue
3) again yes

But you missed one
4) if the tape is write protected and it picks it for a backup, loads it
in the drive and sees that it is write protected it will freeze the
tape.  This does not mean that the tape is bad.  This happens to me some
times if I am doing a restore and it is still running when I go home for
the night.  The restore could finish and the backups could the choose it
for a restore.  When I remember this I will try to suspend the tape
before I go home to it will not choose it and freeze it.  So whenever I
do get notice of a frozen tape I check to see if it was write protected
for a restore before I tag the tape as bad.

-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Heathe
Kyle Yeakley
Sent: Wednesday, September 02, 2009 8:25 AM
To: Veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Frozen Tapes

Hello, I had a question on Frozen media.

First, am I correct in saying that the criteria NetBackup uses to
determine if it should freeze a tape is:

1) NetBackup detects Non-NetBackup data format (So data was written
using straight Unix tar, pax, cpio, or a non-NetBackup commercial app
like Tivoli or Networker)

2) NetBackup detects that there is NetBackup data on the tape, but it's
catalog data, and so it freezes the tape to ensure that the catalog
files aren't overwritten.

3) NetBackup tried to read/write to the tape and experienced more that 3

read/write errors within a 12 hour span of time.

Assuming I'm correct so far, then is the proper method of
troubleshooting Frozen media to:

1) Ensure there isn't some catalog data on the tape.

2) Ensure that the tapes aren't from some other commercial backup
product environment's tape pool (for those of you running multiple
commercial backup applications at a single site).

3) Make sure your tape drives have been cleaned recently.

4) Use bpmedia -m <media id> -unfreeze to unfreeze the tape(s), make a
note of the tape you're unfreezing, and leave it in the scratch pool to
see if it gets used for tonight's backups.

Now for my question: Assuming I was correct on my selection criteria and

my troubleshooting steps, am I correct in saying that if I came in
tomorrow and that media from step 4 was frozen a second time, that it
indicates that the media is more than likely defective? Is there any
other troubleshooting steps anyone would care to add?

Thanks.

- Heathe Kyle Yeakley
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