Drives can go write disabled when they have received too many errors.
Last time I saw this EMC told me it was a hardware issue, Hardware told
me it was a software issue.

It ended up tape drivers/firmware mismatch 
Or EMC Tech Support 1 vs ADIC Tech Support 0

Make sure all tape drivers have the same firmware and drivers loaded.

Note I did NOT say the "latest" we actually had to downgrade two levels
to find a version that was stable on our configuration. This is ONE
possibility I hope this helps. /ALE

> From: EMC NetWorker discussion 
> 
> I have a strange problem. My backups largely work o.k. but 
> some drives go Write Disabled overnight after backups. I have 
> 7 drives and it seems to effect different drives randomly. 
> Frustratingly there is nothing in the daemon.log which seems 
> to point to when the drives go write disabled or why. 
> 
> Any help gratefully recieved. 

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
wit 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