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Duplicate: didn't compare at offset 40 in stream data


awahle

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I'm not sure if this is possibly a bug in Retrospect Express 6.0.222 (driver 3.6.104, WinXP-pro SP1) or in the NTFS compression, or I'm doing something wrong.

 

I have an NTFS-formatted drive and use the duplicate functionality to keep a backup on an external USB-Maxtor OneTouch disk, which is also formatted in NTFS. Compression is switched on for both drives. Occasionally, the message "didn't compare at offset 40 in stream data" appears during the comparison run, which is always at offset 40 and reproducible for any given file for which the message is displayed. However, when manually comparing these respective files (e.g., using cygwin's cmp), it says that both files are identical. When I run the duplicate without compression, it works correctly and no message appears.

 

Anybody encountered a similar behavior or knows about its details?

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Hi

 

It sounds like a read or write failure to me. Retrospect isn't really aware of the compression on the disks. It just sends the files to the proper location and the OS handles it from there. You might want to disable the write cache on the USB drive as a precaution.

 

Thanks

Nate

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Nate, thanks for your response. I'm not quite sure if it is simply a physical read/write error, this wouldn't explain why:

 

 

 

- the problem occurs only in compressed files,

 

- I do not see any messages in the XP event logs,

 

- it only occurs with Retrospect, other comparison tools show no difference, no errors,

 

- and it always occurs at an offset of 40 (what is special about this location?).

 

 

 

Anyway, I will run a full checkdisk on the USB drive to make sure that it is ok. Other than that error message from Retrospect, I didn't encounter any problems.

 

 

 

A.

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An update: checkdisk did not find any errors or bad blocks, and no I/O error was reported - for now it seems to be safe to simply ignore these messages, but it nevertheless would be good to know what they mean ... any additional input is appreciated!

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