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VXA tape flaw



 
 
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  #1  
Old January 26th 04, 09:38 PM
Arthur Begun
external usenet poster
 
Posts: n/a
Default VXA tape flaw

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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.
  #2  
Old January 26th 04, 10:48 PM
Rob Turk
external usenet poster
 
Posts: n/a
Default

"Arthur Begun" wrote in message
om...
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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.


Ehhh?!? Don't know where you get your information from, this is absolute
rubbish.

If you do a backup and your computer freezes halfway into the backup, the
session in progress will most likely not be valid. This is the case with any
backup, regardless if it's tape or CD/DVD, and regardless of the type of
tape drive you use. Backup software usually write their index to tape after
completion of the backup session. If this fails, that specific session will
most likely be invalid. Any previous sessions will be perfectly readable.

Rob (who works for Exabyte)


  #3  
Old January 27th 04, 03:24 AM
Arthur Begun
external usenet poster
 
Posts: n/a
Default

"Rob Turk" wrote in message l.nl...
"Arthur Begun" wrote in message
om...
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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.


Ehhh?!? Don't know where you get your information from, this is absolute
rubbish.

If you do a backup and your computer freezes halfway into the backup, the
session in progress will most likely not be valid. This is the case with any
backup, regardless if it's tape or CD/DVD, and regardless of the type of
tape drive you use. Backup software usually write their index to tape after
completion of the backup session. If this fails, that specific session will
most likely be invalid. Any previous sessions will be perfectly readable.

Rob (who works for Exabyte)



I get my information from personal experience. My tape is now
effectively blank because the header was erased and if you take time
to search the archives of the Retrospect backup software group you
will find that my case is not the first. There is a complaint as far
back as 2001 and a response from Excrix that anyone who has the
problem should contact their technical support. I contacted Exabyte
(their successor) and was given a "so sad, too bad" response.
  #4  
Old January 27th 04, 03:38 AM
Arthur Begun
external usenet poster
 
Posts: n/a
Default

"Rob Turk" wrote in message l.nl...
"Arthur Begun" wrote in message
om...
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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.


Ehhh?!? Don't know where you get your information from, this is absolute
rubbish.

If you do a backup and your computer freezes halfway into the backup, the
session in progress will most likely not be valid. This is the case with any
backup, regardless if it's tape or CD/DVD, and regardless of the type of
tape drive you use. Backup software usually write their index to tape after
completion of the backup session. If this fails, that specific session will
most likely be invalid. Any previous sessions will be perfectly readable.

Rob (who works for Exabyte)



Here is the 2001 post from someone else who lost his VXA header:

http://www.mail-archive.com/retro-ta.../msg02723.html

In my case a hard reboot was enuf to ruin the header and effectively
the 27 gigs of backup on the tape.
  #5  
Old January 27th 04, 09:40 AM
Rob Turk
external usenet poster
 
Posts: n/a
Default

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

l.nl...
"Arthur Begun" wrote in message
om...
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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.


Ehhh?!? Don't know where you get your information from, this is absolute
rubbish.

If you do a backup and your computer freezes halfway into the backup,

the
session in progress will most likely not be valid. This is the case with

any
backup, regardless if it's tape or CD/DVD, and regardless of the type of
tape drive you use. Backup software usually write their index to tape

after
completion of the backup session. If this fails, that specific session

will
most likely be invalid. Any previous sessions will be perfectly

readable.

Rob (who works for Exabyte)



Here is the 2001 post from someone else who lost his VXA header:

http://www.mail-archive.com/retro-ta.../msg02723.html

In my case a hard reboot was enuf to ruin the header and effectively
the 27 gigs of backup on the tape.


What you describe has nothing to do with 'scsi controller wiping out' a
header. It's a condition where the tape drive is powered down during write,
resulting in an inconsistent tape format. Powering down in the middle of a
write session is not a good idea for any data recording device. CompactFlash
can be destroyed by this, CD-RW and DVD-RW is ruined by it, tape drives end
up with incomplete or inconsistent data formats and harddisks may develop
bad sectors from it. This isn't a VXA flaw, it's a "don't do this" common
sense issue.

For your information, should this happen again, the drive is equipped to
detect this condition and has built-in recovery for it. It may take a while,
as the drive needs to read the tape from the begin up to where the write was
terminated by a power loss.

Please note that this recovery re-validates the tape on a block level. It
doesn't mean Retrospect will be able to read from the tape, as it may not be
able to deal with half-a-backup. That's not a device flaw, that's a software
design choise. Retrospect (or any other backup software I know of) isn't
designed to deal with this. Data recovery companies can help you out if they
know the Retrospect format. Your other option is to erase the tape and
re-run your backup.

I find it interesting to see that you post your comment to several
newsgroups on an issue that happened in 2001. Do you also write messages to
car interest groups warning them about Ford because you heard about someone
owning a Pinto?? Do you happen to work for a competitor of Exabyte?

Rob


  #6  
Old January 27th 04, 04:03 PM
Arthur Begun
external usenet poster
 
Posts: n/a
Default

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

l.nl...
"Arthur Begun" wrote in message
om...
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
is written, there is a great chance that the scsi controller version
will wipe out the header and all of the gigs of previous backups on
the tape might as well be gone. It costs thousands to retrieve the
data, and Exabyte will do nothing but give you a list of companies
that recover lost files. After it happened to me I did a google
search and found a post from someone else who suffered the same plight
from 2001 so they have known about the problem since then.

Ehhh?!? Don't know where you get your information from, this is absolute
rubbish.

If you do a backup and your computer freezes halfway into the backup,

the
session in progress will most likely not be valid. This is the case with

any
backup, regardless if it's tape or CD/DVD, and regardless of the type of
tape drive you use. Backup software usually write their index to tape

after
completion of the backup session. If this fails, that specific session

will
most likely be invalid. Any previous sessions will be perfectly

readable.

Rob (who works for Exabyte)



Here is the 2001 post from someone else who lost his VXA header:

http://www.mail-archive.com/retro-ta.../msg02723.html

In my case a hard reboot was enuf to ruin the header and effectively
the 27 gigs of backup on the tape.


What you describe has nothing to do with 'scsi controller wiping out' a
header. It's a condition where the tape drive is powered down during write,
resulting in an inconsistent tape format. Powering down in the middle of a
write session is not a good idea for any data recording device. CompactFlash
can be destroyed by this, CD-RW and DVD-RW is ruined by it, tape drives end
up with incomplete or inconsistent data formats and harddisks may develop
bad sectors from it. This isn't a VXA flaw, it's a "don't do this" common
sense issue.

For your information, should this happen again, the drive is equipped to
detect this condition and has built-in recovery for it. It may take a while,
as the drive needs to read the tape from the begin up to where the write was
terminated by a power loss.

Please note that this recovery re-validates the tape on a block level. It
doesn't mean Retrospect will be able to read from the tape, as it may not be
able to deal with half-a-backup. That's not a device flaw, that's a software
design choise. Retrospect (or any other backup software I know of) isn't
designed to deal with this. Data recovery companies can help you out if they
know the Retrospect format. Your other option is to erase the tape and
re-run your backup.

I find it interesting to see that you post your comment to several
newsgroups on an issue that happened in 2001. Do you also write messages to
car interest groups warning them about Ford because you heard about someone
owning a Pinto?? Do you happen to work for a competitor of Exabyte?

Rob



In case it is not clear to you, the incident happened this past Friday
(1/23/04), not in 2001. When it happened on Friday I talked with
Marty at Exabyte and sent in a log. On Monday I got a call and was
told if the header is gone, tough luck. I was actually using 4.21 of
Backup Exec (not Retrospect) but when the tape that was previously
full of differential backups suddenly turned empty after a backup
froze while writing the header I called Exabyte and also searched
using Google to see if I could find anything else about retrieving the
lost data. I found the 2001 post of someone having a similar problem
using a VXA drive and Retrospect. On the one hand you guys claim that
your drives are more reliable than other formats but as it turns out a
simple software freeze while writing the header blows the header away
and effectively erases the contents of a backup tape unless it is
restored by a data recovery company at the cost of thousands of
dollars.

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.
  #7  
Old January 27th 04, 07:55 PM
Rob Turk
external usenet poster
 
Posts: n/a
Default

"Arthur Begun" wrote in message
om...

In case it is not clear to you, the incident happened this past Friday
(1/23/04), not in 2001. When it happened on Friday I talked with
Marty at Exabyte and sent in a log. On Monday I got a call and was
told if the header is gone, tough luck. I was actually using 4.21 of
Backup Exec (not Retrospect) but when the tape that was previously
full of differential backups suddenly turned empty after a backup
froze while writing the header I called Exabyte and also searched
using Google to see if I could find anything else about retrieving the
lost data. I found the 2001 post of someone having a similar problem
using a VXA drive and Retrospect. On the one hand you guys claim that
your drives are more reliable than other formats but as it turns out a
simple software freeze while writing the header blows the header away
and effectively erases the contents of a backup tape unless it is
restored by a data recovery company at the cost of thousands of
dollars.

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.


It was indeed not clear to me that this happened recently, as all you
referred to was something you found on Google from back in 2001. I called
the engineer you talked to on friday, he forwarded all information. It
describes that you had a failed harddisk, moved the tape drive to a
different system on which you had a bad SCSI connector or cable. The
computer froze while the backup software was rewriting it's header
information on a tape that contained the only backup of the failed disk, to
which you decided to append to when you should have write protected that
tape and used a fresh tape.

I'm not sure how I can explain this any clearer. What you experienced,
regardless of the backup package you used, is that a backup failed in a way
that left an incomplete backup set or incomplete index information on tape.
To the tape drive, all data blocks it was told to write are actually there.
All blocks that were there before from previous backups are also on that
tape. However, when BackupExec tries to examine that tape, it *expects* a
certain sequence to be present on the tape. The sequence consists of a
number of filemarks and data blocks of predetermined size, all in a closely
defined order. If, for whatever reason, that *exact* sequence is not found
on the tape, BackupExec (and most other backup software) will assume this is
either an empty tape, or a foreign tape written in some other format and
refuse to process it.

There are two levels of 'header' in play. One header is under control of the
drive, and is invisible to the user. It lives in the first section of tape
even before where data ever gets written. The drive uses it to to
'bookkeeping'. That's the header I referred to when I mentioned
auto-recovery in my previous post.

The second header is the high-level format as it's defined by your backup
software. To the tapedrive these are just data blocks. To your backup
application it's a crucial section on tape. If power is cut, or the system
freezes or reboots while that header is being written, your backup
application will no longer recognise the tape or what's on it. This is NOT
the tape drive's issue. The tape drive doesn't know about the format, it
just writes the blocks it receives from the host. If the host stops sending
blocks, the drive stops writing them. If that means you have half an index
file, that's too bad, but nothing the tape drive can do anything about.

Compare it to harddisk technology. If you write a file, and you lose power
before the FAT/NTFS directory is written, you may lose that file and perhaps
more if bad luck strikes. That's not the fault of Maxtor, Seagate, Hitachi
or WD, and no-one will blame the harddisk manufacturer for this. In the same
sense, while your backup software is updating it's header, if you lose
power, you may lose normal access to the data as well. There's nothing VXA,
DDS, DLT, LTO, Magstar, OnStream, AIT, SLR on any other tape technology on
this planet can change about that.

So let me re-iterate this one last time:
- Are your previous backups still on the tape? YES
- Can your standard backup software reach it? NO
- Can a data recovery company get to the data? PERHAPS.
- Is this VXA's fault in any way? NO.

The engineer you talked to on friday gave you the right advice. Your data
can most likely be rescued, get in touch with a data recovery company.
Meanwhile, VXA is not to blame for this in any way.

Rob


  #8  
Old January 27th 04, 07:59 PM
Rob Turk
external usenet poster
 
Posts: n/a
Default

"Peter" wrote in message
...

"Rob Turk" wrote

What you describe has nothing to do with 'scsi controller wiping out' a
header. It's a condition where the tape drive is powered down during

write,
resulting in an inconsistent tape format. Powering down in the middle of

a
write session is not a good idea for any data recording device.

CompactFlash
can be destroyed by this, CD-RW and DVD-RW is ruined by it, tape drives

end
up with incomplete or inconsistent data formats and harddisks may develop
bad sectors from it. This isn't a VXA flaw, it's a "don't do this" common
sense issue.


Can the tape drive re-write the tape so it can be re-used?

I know from years of using DDS2/DDS3 and now DDS4 that this sort of
thing can make a tape unusable.


Peter.
--


Yes it can. You can just insert the tape and start writing if it comes up as
blank, or first erase it if your backup software thinks there's an unknown
format on it.

Rob


  #10  
Old January 28th 04, 05:00 AM
Arthur Begun
external usenet poster
 
Posts: n/a
Default

"Rob Turk" wrote in message .nl...
"Arthur Begun" wrote in message
om...

In case it is not clear to you, the incident happened this past Friday
(1/23/04), not in 2001. When it happened on Friday I talked with
Marty at Exabyte and sent in a log. On Monday I got a call and was
told if the header is gone, tough luck. I was actually using 4.21 of
Backup Exec (not Retrospect) but when the tape that was previously
full of differential backups suddenly turned empty after a backup
froze while writing the header I called Exabyte and also searched
using Google to see if I could find anything else about retrieving the
lost data. I found the 2001 post of someone having a similar problem
using a VXA drive and Retrospect. On the one hand you guys claim that
your drives are more reliable than other formats but as it turns out a
simple software freeze while writing the header blows the header away
and effectively erases the contents of a backup tape unless it is
restored by a data recovery company at the cost of thousands of
dollars.

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.


It was indeed not clear to me that this happened recently, as all you
referred to was something you found on Google from back in 2001. I called
the engineer you talked to on friday, he forwarded all information. It
describes that you had a failed harddisk, moved the tape drive to a
different system on which you had a bad SCSI connector or cable. The
computer froze while the backup software was rewriting it's header
information on a tape that contained the only backup of the failed disk, to
which you decided to append to when you should have write protected that
tape and used a fresh tape.

I'm not sure how I can explain this any clearer. What you experienced,
regardless of the backup package you used, is that a backup failed in a way
that left an incomplete backup set or incomplete index information on tape.
To the tape drive, all data blocks it was told to write are actually there.
All blocks that were there before from previous backups are also on that
tape. However, when BackupExec tries to examine that tape, it *expects* a
certain sequence to be present on the tape. The sequence consists of a
number of filemarks and data blocks of predetermined size, all in a closely
defined order. If, for whatever reason, that *exact* sequence is not found
on the tape, BackupExec (and most other backup software) will assume this is
either an empty tape, or a foreign tape written in some other format and
refuse to process it.

There are two levels of 'header' in play. One header is under control of the
drive, and is invisible to the user. It lives in the first section of tape
even before where data ever gets written. The drive uses it to to
'bookkeeping'. That's the header I referred to when I mentioned
auto-recovery in my previous post.

The second header is the high-level format as it's defined by your backup
software. To the tapedrive these are just data blocks. To your backup
application it's a crucial section on tape. If power is cut, or the system
freezes or reboots while that header is being written, your backup
application will no longer recognise the tape or what's on it. This is NOT
the tape drive's issue. The tape drive doesn't know about the format, it
just writes the blocks it receives from the host. If the host stops sending
blocks, the drive stops writing them. If that means you have half an index
file, that's too bad, but nothing the tape drive can do anything about.

Compare it to harddisk technology. If you write a file, and you lose power
before the FAT/NTFS directory is written, you may lose that file and perhaps
more if bad luck strikes. That's not the fault of Maxtor, Seagate, Hitachi
or WD, and no-one will blame the harddisk manufacturer for this. In the same
sense, while your backup software is updating it's header, if you lose
power, you may lose normal access to the data as well. There's nothing VXA,
DDS, DLT, LTO, Magstar, OnStream, AIT, SLR on any other tape technology on
this planet can change about that.

So let me re-iterate this one last time:
- Are your previous backups still on the tape? YES
- Can your standard backup software reach it? NO
- Can a data recovery company get to the data? PERHAPS.
- Is this VXA's fault in any way? NO.

The engineer you talked to on friday gave you the right advice. Your data
can most likely be rescued, get in touch with a data recovery company.
Meanwhile, VXA is not to blame for this in any way.

Rob



I appreciate your going explaining more detail about the header and
your getting the information (though it was a bit convoluted) from my
support call to Marty. At this point in time, I have no evidence that
there was a cable or SCSI card problem. All I know is that the
computer froze up and it could have been just a software problem. In
any case, 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 and the machine froze up and after rebooting all of the
information on the tape was inaccessible. That is what I was warning
people of and that is what happened. I feel a warning was mandated
because of Exabytes claims regarding how more reliable the VXA drives
are compared to other systems. I've used Backup Exec in various
versions for close to 2 decades and have never loss more than a single
file before. Suddenly with this drive that is supposed to be extra
reliable, a whole tape is wiped out. Seems pretty odd to me.

On top of that, in talking with the restoration services suggested by
Marty, the one that specializes in tape told me that they have been
unable to automate the recovery of VXA tape which makes their service
extraordinarily expensive when needed.
 




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