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VXA tape flaw



 
 
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  #22  
Old January 29th 04, 05:08 PM
Arthur Begun
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You might be interested in reading this link:

http://www.mail-archive.com/retro-ta.../msg02793.html

It is a post from Ecrix (the previous manufacturer of VXA drives) and
describes the unusual way VXA drives handle power and other
interruptions. Seems to me that the intended improvement could be
causing the problem.

As far as Backup Exec causing the problem, I doubt it. Since it
recognized that an error occurred and displayed an error message, I
doubt it was writing anything further to the tape.

People do appended backups all the time. I've only heard of 2 cases
where doing so effectively wiped out the contents of a tape. In both
cases a VXA drive was being used.
  #23  
Old January 29th 04, 07:28 PM
Paul Rubin
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(Arthur Begun) writes:
You might be interested in reading this link:

http://www.mail-archive.com/retro-ta.../msg02793.html

That is about an entirely different issue.

As far as Backup Exec causing the problem, I doubt it. Since it
recognized that an error occurred and displayed an error message, I
doubt it was writing anything further to the tape.


The error message that it displayed, from what I can tell, was because
the data that it read back wasn't valid for its own format. In
particular a block at the beginning of the tape had gotten trashed
when the computer hung. As far as I can tell, all the other blocks
could still be read.

People do appended backups all the time.


Maybe other people do appended backups, but that's not what you did.
Your backup involved changing a central header area at the beginning
of the tape, not just appending.

I've only heard of 2 cases where doing so effectively wiped out the
contents of a tape.


No. You've heard of either zero or one cases. Your case was not an
append backup. I don't know what the other person's was.
  #24  
Old January 29th 04, 10:49 PM
Arthur Begun
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Paul Rubin wrote in message ...
(Arthur Begun) writes:
After Backup Exec backups the files, it writes to the header. I
presume it adds some information to the front that tells the tape
where the last backup began and ended. Seems to me that if this
operation was interupted, the newly appended backup would expected to
be lost but information on previous backups should not be wiped out.


That would depend on the contents of the header, which is up to the
software, not the tape drive.

Unfortunately the next time the tape was read it read as being blank.
The makers of the drive says it is Backup Exec's fault.


So far, all indications I've seen are that the makers of the drive are
correct. Either the hardware can read back all the blocks that Backup
Exec wrote to the drive (possibly excepting a few trashed blocks from
where the computer crashed) or it can't. If it can, any further
problems fall squarely on the backup software.

Perhaps it is but it never happened to me with any other brand drive
and at least one other person had the same experience back in 2001
with his VXA drive according to his archived post. And he was using
Retrospect, not Backup Exec. Seems strange that 2 different
software packages presented the same problem to 2 different users
and the only common denominator was that it was with the same brand drive.


Perhaps both users were making the same mistake, which is trying to
re-use a live critical tape without having another one they can fall
back to. You should never re-use a backup tape until you have a
useable backup on a different tape...



Just in case anyone is reading this thread, check this guys posts in
Google. Basically he is a troll. And if the VXA format is not
capable of reliable appended backups, that fact should be specified in
documentation.
  #26  
Old January 29th 04, 11:15 PM
Lynn McGuire
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If you are considering a VXA tape drive from exabyte (formerly ecrix)
you should be aware of a fatal flaw. Even though ads show a tape
soaking in a cup of coffee and a claim that the data is still
recoverable, the tape header is extremely fragile. If you are doing a
backup and the computer freezes and requires a hardboot as the header


Rule #1 - one tape, one backup (do not put mutiple backups on one tape)

Rule #2 - one backup, one tape (buy a big enough tape drive for your backup)

Rule #3 - use multiple backup devices like hard drives in addition to your
tape drive - that way the single point of failure (the tape) will
not kill you

We use a weekly backup to a VXA-2 tape drive in addition to three
200 GB hard drives that are daily backed up to on the network. Only
one of the hard drives is on the file server.

Lynn


  #28  
Old January 30th 04, 05:05 AM
Arthur Begun
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"Lynn McGuire" wrote in message ...
If you are considering a VXA tape drive from exabyte (formerly ecrix)
you should be aware of a fatal flaw. Even though ads show a tape
soaking in a cup of coffee and a claim that the data is still
recoverable, the tape header is extremely fragile. If you are doing a
backup and the computer freezes and requires a hardboot as the header


Rule #1 - one tape, one backup (do not put mutiple backups on one tape)

Rule #2 - one backup, one tape (buy a big enough tape drive for your backup)

Rule #3 - use multiple backup devices like hard drives in addition to your
tape drive - that way the single point of failure (the tape) will
not kill you

We use a weekly backup to a VXA-2 tape drive in addition to three
200 GB hard drives that are daily backed up to on the network. Only
one of the hard drives is on the file server.

Lynn


So if your building burns down goodbye data.

By the way, some of the obnoxious posts here assumed my data was life
or death, etc, etc, etc. It was not. Life or death data is on a
mirrored file server and backed up to tape. This data was from a
workstation. According to statistics passed around by magazines, 80%
of companies don't backup workstations at all. I did. And it
concerns me that somehow when a backup was appended to media, the end
result was the loss of all previous backups. Been using Backup Exec
for almost 2 decades and never have seen it before. And for many
years that was using some very primitive drives from Colorado, Conner,
and others. VXA promotes itself as more reliable than others yet
magically a tape is wiped out. And mine wasn't the only one according
to the 2001 post by a Retrospect user.
 




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