[CentOS] sg device

Sat Dec 10 20:28:56 UTC 2005
Tony Schreiner <schreian at bc.edu>

What is the "sg" device?

The reason I ask, is that I have a file server running CentOS 4.2 on  
a Dell Precision 1650. Disks are attached via QLogic FC. I backup to  
a Qualstar TLS-4222 tape changer, with AIT-2 tapes, which is  
connected over an Adaptec 29160 Ultra 160 SCSI. The software I'm  
using is Legato Networker version 7.1.2. I'm backing up a bit under 1  
TB a month with this.

Quite frequently these days (meaning once a month or two), the  
Networker software loses the ability to control the tape changer.  
Mount, unmount commands just don't work any more. The only way I can  
seem to fix it, is to use the Networker admin software to remove the  
robot, and tape device, and then recreate it with the Networker  
jbconfig command.

The jbconfig command detects the Qualstar, and then detects /dev/sg3  
as the tape device. Now Networker can use this device to move tapes  
around in the robot, but not to read and write. So I have to delete / 
dev/sg3 from the Networker configuration, and then add /dev/nst0. And  
then it works (for a while).

So I'm wondering, why the software is setting me up with /dev/sg3  
instead of /dev/nst0; and is there anything I can do about it. Bonus  
question if anyone else had a similar issue.

Thanks,
Tony Schreiner
Boston College