>>>>> On Mon, 06 Jun 2011 14:24:48 +0100, Alan Brown said:
> 
> What kind of tape media are you using? (DDS, DAT, DLT, LTO, etc)

All but one was with DDS4 that we no longer use (yes, I know).

Some of the errors were bugs in Bacula's EOT handling though, so not directly
related to the media type.


> LTOs verify the data on trailing read heads and rewrite any failures on 
> the fly.

I'm using LTO-1 now and I've had only one situation where a backup got an
uncorrected write error.  Worryingly, the job itself didn't detect the
failure, but TapeAlert showed it and the next job failed completely.  Also
verifies of that tape failed on jobs that had *not* reported write errors,
though it is possible that the write error left the drive in a funny state.

Do you look at the error counters from TapeAlert?  I always get "fast" ECC
correction even with new tapes, but I've never known if that is normal or not.

E.g. smartctl after writing 35GB:

Alert: Error counter log:
Alert:            Errors Corrected by           Total   Correction     
Gigabytes    Total
Alert:                ECC          rereads/    errors   algorithm      
processed    uncorrected
Alert:            fast | delayed   rewrites  corrected  invocations   [10^9 
bytes]  errors
Alert: read:          0        0         0         0          0          0.000  
         0
Alert: write:      1095        0         0         0       1194          0.000  
         0

and after verifying it:

Alert: Error counter log:
Alert:            Errors Corrected by           Total   Correction     
Gigabytes    Total
Alert:                ECC          rereads/    errors   algorithm      
processed    uncorrected
Alert:            fast | delayed   rewrites  corrected  invocations   [10^9 
bytes]  errors
Alert: read:        628        0         0         0        628          0.000  
         0
Alert: write:      1095        0         0         0       1194          0.000  
         0

__Martin

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