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Help - accidentally erased the wrong tape


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I'm using Retrospect 6.1.138 on Mac OS X 10.4.9 with an Exabyte VXA-320 1x10 storage loader.

 

For some reason, Retrospect's view of which tape was in which slot got corrupted. I erased what I thought was a blank (but mis-labeled) tape, according to the device window, and it turns out that I erased a member of a data set that had important data on it. Retrospect apparently thought it was a harmless operation, due to the incorrect view of the library slots, so it didn't warn me.

 

I have a backup of the storage set file, but Retrospect thinks the tape doesn't exist anymore. Is there any way to convince Retrospect that this tape isn't erased and to just ignore its header? I figure it's a long shot, but I have to ask. Of course, the one tape I erased is the one that I actually need to restore from!

 

Thanks,

-Mike

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A tape will only show erased if the hardware tells Retrospect it is erased.

Respectfully, Robin, I disagree with you on this. See the bug report I turned in on this a couple of years ago under our support contract, and the bug still exists. Retrospect will report a tape as erased if it encounters an error at BOT or on tape insertion if not at BOT (at least on an Exabyte VXA-2 1x10 1u PacketLoader (SCSI) and several other drives - see numerous posts by me and others in these forums, too). Sometimes, if you do a cleaning cycle, then quit and restart Retrospect, it will decide that the tape is not erased.

 

If you have erased the tape, then only data recovery services can help you.

I agree with you on this one.

 

Russ

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Retrospect will report a tape as erased if it encounters an error at BOT or on tape insertion if not at BOT (at least on an Exabyte VXA-2 1x10 1u PacketLoader (SCSI) and several other drives - see numerous posts by me and others in these forums, too). Sometimes, if you do a cleaning cycle, then quit and restart Retrospect, it will decide that the tape is not erased.

 

It is true the tape can show up erased when it isn't actually erased, but it is still the hardware reporting to Retrospect the state of that tape. If "you do a cleaning cycle, then quit and restart Retrospect", then your hardware has reset itself, displaying the correct tape header.

 

If an error is encountered reading the tape header, that is not normal or good. This error may cause the hardware to then tell Retrospect the inserted media is erased. Different drive types have different thresholds for read errors and can do better error correction then others

 

Retrospect will never report an inserted tape as erased unless the hardware itself has failed or is incorrectly displaying the tape header. As a result, the user may think an erased tape is inserted and then manually erase the tape...resulting in data loss.

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Retrospect will never report an inserted tape as erased unless the hardware itself has failed or is incorrectly displaying the tape header.

Well, we will just have to disagree on this point. See my original bug report a couple of years ago when this behavior (tape incorrectly shown as erased) was caused by an extended power failure during a Retrospect verify pass (server shut down cleanly but Retrospect left the tape not rewound) causing the tape not to be left at BOT, causing the tape to be indicated as "erased", causing Retrospect's failure to honor names of pre-named, pre-erased barcoded tapes to overwrite the tape when it needed new media for another backup set. This is why I requested that a preference be added to "rewind on start" to eliminate this data destruction again, but it's never been added and I've never seen it on a feature list for upcoming releases. I will keep asking until it appears. This dangerous behavior of Retrospect, namely, the failure to use a pre-named, pre-erased barcoded tape of the proper member name when it is looking for new media, and instead it's decision to choose arbitrarily whatever "erased" tape it finds in the autoloader, regardless of barcode and other properly-named tapes in the autoloader, coupled with this improper classification of tapes as "erased", is serious, and has needed to be addressed for years. It was fixed years ago in the Windows version, but never in the Mac version.

As a result, the user may think an erased tape is inserted and then manually erase the tape...resulting in data loss.

See above - it's not always user error. It's a design flaw in Retrospect.

 

Russ

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Well, we will just have to disagree on this point.

 

I think you are right on that :) I know you have used VXA, and it does act a little different from all other tape devices (I am not sure why).

 

Before Retrospect can write to any tape after opening Retrospect or loading a tape into the drive, it must read the header of the tape to get the tape name. Retrospect can not start writing to a tape until the tape header is found. Now, if you cancel a backup and start the backup again, it is possible that Retrospect could assume the tape has not changed and continue from the last EOD marker on the tape.

 

if you have a Power Failure with the tape in the drive, the next time you open Retrospect, the software sends a command to the hardware to read the tape header. It is then up to the hardware to display this tape header.

 

With a tape library, Retrospect will sometimes confuse the name associated with a specific bar code, but once that tape gets loaded into the physical tape drive, the name displayed will correspond with the name reported by the tape header, and the name associated with the bar code is no longer important. A bug does exist, which can cause Retrospect to display the wrong name, once the tape is moved back into the library slot.

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With a tape library, Retrospect will sometimes confuse the name associated with a specific bar code, but once that tape gets loaded into the physical tape drive, the name displayed will correspond with the name reported by the tape header, and the name associated with the bar code is no longer important. A bug does exist, which can cause Retrospect to display the wrong name, once the tape is moved back into the library slot.

 

Are there any plans to fix this bug? I'm pretty sure this bug is what caused me to accidentally erase the wrong tape.

 

Back to my original question - I was hoping there was some way to manually re-write or skip the tape header that gets erased when you do a manual quick erase, but it sounds like the only way to do that is with professional data recovery. Thanks for all the responses. The lesson I learned is to always load the tape into the drive to determine its label and not to trust the labels listed in the library slots.

 

-Mike

 

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If you move a tape from Slot X into the tape drive, the name displayed will be the true and actual name of that tape. If you suspect a problem, you can try to clear the library slot info using http://kb.dantz.com/article.asp?article=7901&p=2 or you can remove the Retrospect preferences to reset the barcode info

 

The library display issue will get fixed when we switch to the new codebase for Retrospect X. It utilizes device code found on Windows, that does not exhibit this behavior.

 

DriveSavers or is your best bet for tape recovery after an erase.

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Back to my original question - I was hoping there was some way to manually re-write or skip the tape header that gets erased when you do a manual quick erase, but it sounds like the only way to do that is with professional data recovery. Thanks for all the responses. The lesson I learned is to always load the tape into the drive to determine its label and not to trust the labels listed in the library slots.

Mike,

 

The problem is that tape blocks are not written in fixed places on the tape, as happens with disks, which have servo tracks, and which are pre-formatted. With tapes, the data just starts appearing, and lasts as long as the block goes. You can only append to tape after the end of tape, and can't put anything in the middle. There's just no way to get the block you write to end up at the same place the original block ended. The first block doesn't always start in exactly the same place, either.

 

You are hosed.

 

Russ

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