VXA tape flaw

Malcolm Weir wrote in message . ..
On 27 Jan 2004 07:03:25 -0800, (Arthur Begun)
wrote:

[ Snip ]

So to make it absolutely clear, the incident happened afew days ago.
I have a tape on my desk full of data that is inaccessible because
somehow the header was destroyed because software froze while
appending a backup. I consider it a major flaw. I've been doing
backups on tape for almost 2 decades and have never seen a header
destroyed by an appended backup.

Why, *exactly* did you reset the system while the tape drive was
writing something?

Malc.


The tape drive was not writing anything. The machine was locked up
with an error message on it. The software said there was an error.
The machine was locked up. Nothing much left to do but stare at it or
reboot. The error did not appear severe or strange.... and
unfortunately I did not write it down. I do know it happened after
the files backup was done but before verification process started so I
presume it was writing the header which was wiped out. I've been
using this same drive with the same software for years for appending
backups to various tapes. Now it seems that if it hits an error at
the right time chances are the contents of a tape will be wiped out.
Seems to me that since the software knew it had hit an error, it would
have stopped writing and the problem was that the drive somehow left
things in a dangerous way.

(Arthur Begun) writes:

Backup Exec backed up about 4 gigs and was to append the
backup to the tape and instead, while accessing the header something
went wrong

So it sounds like your earlier description of an append-only backup
was wrong. Backup Exec was trying to modify the beginning of the
tape, not just append stuff to the end, if I understand correctly now.

and the machine froze up and after rebooting all of the
information on the tape was inaccessible.

Inaccessible to what? To Backup Exec? Can you read raw blocks off
the tape? If yes, you have a Backup Exec problem, not a VXA problem.

Paul Rubin wrote in message ...
(Arthur Begun) writes:

Backup Exec backed up about 4 gigs and was to append the
backup to the tape and instead, while accessing the header something
went wrong

So it sounds like your earlier description of an append-only backup
was wrong. Backup Exec was trying to modify the beginning of the
tape, not just append stuff to the end, if I understand correctly now.

and the machine froze up and after rebooting all of the
information on the tape was inaccessible.

Inaccessible to what? To Backup Exec? Can you read raw blocks off
the tape? If yes, you have a Backup Exec problem, not a VXA problem.

For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank. I've been using Backup Exec in various versions on various
drives for almost 2 decades and have never seen it wipe out a tape
before. Its a first for me and happened on a VXA drive. Seems to me
it is something that VXA users should be aware of. They should have
at least 2 backups of their important backups. When VXA ads claim
that the information on a tape can survive a dip in a hot cup of
coffee, it is not something you would expect. The software seems to
have performed correctly. It reported an error before verification of
the backup. Why the tape now reads as empty is something that I don't
have the time to fully research but other owners need to be aware of
the potential problem.

"Arthur Begun" wrote in message
m...

For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank. I've been using Backup Exec in various versions on various
drives for almost 2 decades and have never seen it wipe out a tape
before. Its a first for me and happened on a VXA drive. Seems to me
it is something that VXA users should be aware of. They should have
at least 2 backups of their important backups. When VXA ads claim
that the information on a tape can survive a dip in a hot cup of
coffee, it is not something you would expect. The software seems to
have performed correctly. It reported an error before verification of
the backup. Why the tape now reads as empty is something that I don't
have the time to fully research but other owners need to be aware of
the potential problem.

Just like owners of a car must be warned that running into a tree may render
their vehicle useless... And do make absolutely clear to them that it's the
tree's fault...

I was about to try one more time, but never mind, this is hopeless. How can
you claim that "The software seems to have performed correctly" when it
*FROZE YOUR SYSTEM* ???

Next time this 'software error' pops up, please call the manufacturer of
your monitor. It's them who are responsible for showing the error in the
first place...

Rob

(Arthur Begun) writes:
For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank.

You do not seem to have your story straight. It still sounds like
Backup Exec changes some stuff at the beginning of the tape when you
do an update. Changing stuff at the beginning is not what most people
call "appending". Appending means adding stuff to the end, not changing
stuff at the beginning.

On 28 Jan 2004 07:03:56 -0800, (Arthur Begun)
wrote:

Inaccessible to what? To Backup Exec? Can you read raw blocks off
the tape? If yes, you have a Backup Exec problem, not a VXA problem.

For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank.

Yet there are clearly failure modes in which that can happen.

I've been using Backup Exec in various versions on various
drives for almost 2 decades and have never seen it wipe out a tape
before.

And how many of those "various drives" have been doing this "append
backup" thing?

One of the mixed blessings of high capacity drives is that people feel
that somehow they should be getting best "value for money" by filling
up the tape using multiple save sets. That's just dumb: one save set
per tape is the best solution, and everything else is a compromise.

Its a first for me and happened on a VXA drive.

Gosh. By the way, note how many threads over the years have reported
problems in their use of Backup Exec. Problems exist with B.E. (and
with most backup packages, to be fair).

Seems to me
it is something that VXA users should be aware of.

Seems to me something that Backup Exec users should be aware of!

They should have
at least 2 backups of their important backups.

Well, DUH!

That applied to users of 7 track tapes FOUR decades ago!

It hasn't changed, and never will.

When VXA ads claim
that the information on a tape can survive a dip in a hot cup of
coffee, it is not something you would expect.

Why? Have you any indication that it wouldn't?

Notice, if you will, that one thing that *isn't* dipped in a cup of
coffee is the computer. This is, therefore, conclusive proof that the
problem must lie in the host computer!

The software seems to have performed correctly.

Errr... no, it doesn't!

It reported an error before verification of
the backup.

Yup. Sounds like it had a problem!

Why the tape now reads as empty is something that I don't
have the time to fully research

I.e. you have no clue, but seem to feel that blaming the drive is
solution. Hmmm.... yet we already know that the user isn't following
best practice.

By the way, media fails. ALL MEDIA.

but other owners need to be aware of
the potential problem.

Which is best characterized as "Don't let that guy manage your
backups!"

Malc.

On 27 Jan 2004 20:20:27 -0800, (Arthur Begun)
wrote:

Malcolm Weir wrote in message . ..
On 27 Jan 2004 07:03:25 -0800, (Arthur Begun)
wrote:

[ Snip ]

So to make it absolutely clear, the incident happened afew days ago.
I have a tape on my desk full of data that is inaccessible because
somehow the header was destroyed because software froze while
appending a backup. I consider it a major flaw. I've been doing
backups on tape for almost 2 decades and have never seen a header
destroyed by an appended backup.

Why, *exactly* did you reset the system while the tape drive was
writing something?

Malc.

The tape drive was not writing anything. The machine was locked up
with an error message on it. The software said there was an error.
The machine was locked up. Nothing much left to do but stare at it or
reboot. The error did not appear severe or strange....

Well, except that it hung the machine...

That sounds rather severe *and* strange!

and
unfortunately I did not write it down. I do know it happened after
the files backup was done but before verification process started so I
presume it was writing the header which was wiped out. I've been
using this same drive with the same software for years for appending
backups to various tapes. Now it seems that if it hits an error at
the right time chances are the contents of a tape will be wiped out.

Yup. Your challenge is to justify the assertion that this phenomenon
applies only to one type of drive...

Seems to me that since the software knew it had hit an error, it would
have stopped writing

Possibly. Possibly it would have, say, sent a SCSI reset...

and the problem was that the drive somehow left things in a dangerous way.

Nope. That's the software's fault....

Malc.

Paul Rubin wrote in message ...
(Arthur Begun) writes:
For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank.

You do not seem to have your story straight. It still sounds like
Backup Exec changes some stuff at the beginning of the tape when you
do an update. Changing stuff at the beginning is not what most people
call "appending". Appending means adding stuff to the end, not changing
stuff at the beginning.

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.
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. 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.

(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. So, perhaps rather than saying
the problem is Backup Exec's fault for writing the wrong stuff to the
tape, it's more correct to say the problem is Arthur Begun's fault for
using stupid and incorrect backup procedures.

"Rob Turk" wrote in message ...
"Arthur Begun" wrote in message
m...

For Backup Exec, append backup means to add the backup to the tape.
It does not mean wipe out the tape and make it read to the software as
blank. I've been using Backup Exec in various versions on various
drives for almost 2 decades and have never seen it wipe out a tape
before. Its a first for me and happened on a VXA drive. Seems to me
it is something that VXA users should be aware of. They should have
at least 2 backups of their important backups. When VXA ads claim
that the information on a tape can survive a dip in a hot cup of
coffee, it is not something you would expect. The software seems to
have performed correctly. It reported an error before verification of
the backup. Why the tape now reads as empty is something that I don't
have the time to fully research but other owners need to be aware of
the potential problem.

Just like owners of a car must be warned that running into a tree may render
their vehicle useless... And do make absolutely clear to them that it's the
tree's fault...

I was about to try one more time, but never mind, this is hopeless. How can
you claim that "The software seems to have performed correctly" when it
*FROZE YOUR SYSTEM* ???

Next time this 'software error' pops up, please call the manufacturer of
your monitor. It's them who are responsible for showing the error in the
first place...

Rob


You seem to ignore the fact that although my tape was wiped out using
Backup Exec, the other guy who complained was using Retrospect. Only
common denominator is we were both using a VXA drive. I've had backup
software lock up plenty over the last 2 decades. It can happen
because of bad media, corrupted file, whatever. Never seen it wipe
out a tape before. Isn't it just possible that you have a problem
that should be investigated rather than just pulling a Microsoft and
attacking the customer?