Hello,
The problem you discriebed happend after adding secound Tape Device to the 
SAN, what if you remove that again, if the tapes do Not display the 
problem after that then you have isolated the problem to that one Tape 
Device,is it possible that the addtional device is causing SCSI\Reset 
errors on the entire SAN Fabric that you are connected to ?
You will need to look for errors on your Hardware-i.e Tape lib, San 
switches etc to isolate bad cable\port, Firmware,HBA settings and\or 
Drivers pins whatever the cause of it.
Any talks about block size, etc are not relavent, this appears to be 
faulty hardware\software\config issues.
Note: It may help to Disable the Faulty Device-Run Test backups-see what 
happens.
then 
Re-enable the new device and watch for the errors to pop up again.
Thanks

To sign off this list, send email to listserv AT listserv.temple DOT edu and 
type "signoff networker" in the body of the email. Please write to 
networker-request AT listserv.temple DOT edu if you have any problems with this 
list. You can access the archives at 
http://listserv.temple.edu/archives/networker.html or
via RSS at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER