Uhh, the error underlying this is that data has been overwritten, and that's 
not recoverable.  
 
SCSI resets will generally be caught by NetWorker and all savesets marked 
suspect anyway.  There is some software out there (regularly for system health 
monitoring, ironically) which will simply try to open tape handles to check 
that things are working and will use things like /dev/rmt/0.  The OS will 
rewind that as soon as it's closed.  There's no error apart from a delay in 
accessing the tape drive during this time (a retryable EBUSY or similar when it 
encounters the file lock).  NetWorker will generally check its position on tape 
before writing, but I'm sure there are a couple of instances where it just 
expects to be in the same place as before.
 
7.3 should get around this, but that means using 7.3.  I'm not sure if its SCSI 
reserve is enabled by default or not.  It won't block a reset, but it will 
block a rewind.  If you're on HP, set the st_no_rewind (I think) kernel 
parameter to disable rewind-on-close devices, but this will only protect SAN 
tape drives in the event that software issuing (effectively) those rewinds is 
running on HP.
 
Cheers,
 
Stuart.

________________________________

From: EMC NetWorker discussion on behalf of Dag Nygren
Sent: Tue 31-Oct-06 16:00
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] Verifying data written



> I believe that drives with a tape mounted but not being written to when a
> bus reset occurs will show an error with scanner along the lines of
> expected file number X got file number X+N.

Probably, but that is a recoverable error as Networker will try to reseek
to end of data.

Best
Dag

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