tape capacity reduction due to defective tapes?

[Wolfgang_Beyer]

I obtained a warning saying that due to some problems the capacity of a tape has been reduced but no data are lost. Is this a permanet capacity reduction at all? Does it has to do with defect parts of tape wich are marked to be no longer used in the future? This error occurs in the last months with increasing incidence.

Somebody told me, that this can happen if I try to save compressed data. I don’t know what compressed data means in this context. I did'nt saved special compressed data but an usual mix of data of many persons containing also "compressed" data like JPG-images from a NTFS partition but without the NTFS compress option activated. Hardware compression of the tape drive was enabled.

Thank you for any hint!

Wolfgang Beyer

[Sharvari_Deshmu]

Hello,

We request you to mention the exact error that you receive?

If you are already using hardware compression then this could happen if the tapes that you are using are old or have been used several times.

we request you to perform a "long erase" operation on the tape that you want to erase and check.

Also perform a full backup until the tape is filled for example if the tape capacity is 30GB then try to perform a backup of 30GB with overwrite option. Once the backup is completed and next time when the tape is inserted for backup, check the media capacity displayed.

Also perform the following:

-Please clean the tape drive according to the hardware manufacturers guidelines.

Please also refer the following technote

http://seer.support.veritas.com/docs/199542.htm



Thanks,

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[Wolfgang_Beyer]

The message translated in englisch is "The tape drive has problems during the process of reading data. No data are lost, but a reduction of tape capacity happened." (in german "Das Bandlaufwerk hat Probleme beim Lesen von Daten. Es sind keine Daten verlorengegangen; es kam jedoch zu einer Verringerung der Bandkapazität."). I obtaine this warning in the protocol file not during the phase of writing data on tape but during the subsequent identity check. In the meantime the frequency of this message is about once every 5 completely overwritten 40GB-tape.

We use a cleaning tape once every month as recommended from the drive manufacturer.

In the meantime I tested the capacity of 4 tapes saving 100MB files (exactly 100*2^20Bytes) containing random numbers until tape overflow. According to this test on 4 tapes with "40GB" capacity of 2 different manufacturer I measured capacities of 28100, 26700, 26700 and 26500MB. The tape with 26500MB was one for wich I obtained earlier such a capacity reduction warning.

Now I just repeat such a capacity measurement before and after a "long erase" operation. I like to report the result as soon as possible.

Thanks so far

[Amruta_Purandar]

Hello,

This is a tape drive error. The drive is having trouble reading the data. For test purposes, try backing up to a backup-to-disk folder and verify the results.

As mentioned these are tape alerts, please contact your hardware vendor for further troubleshooting.

NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.