Confusion about devices rmt, st, sg
Hello everyone,
In solaris I have a confusion for understanding the link between the following tape device notations and netbackup configuration files:
/dev/rmt/*
/usr/openv/volmgr/bin/driver/sg.conf
/usr/openv/volmgr/bin/driver/st.conf
If anyone have a clear understanding I would be grateful if you could share.
Rgds
/dev/rmt are the operating system device files for the tape drive.
The st.conf file is used by the os to map what devices are connected to the bus and how they should be configured.
The sg.conf file is the only NBU file of those you have mentioned.
It is used to build and configure the sg driver.
The sg driver is used to pass various scsi commands to the tape drives (and library) that cannot be sent via the regular os tape device files.
So when a tape command such as mt -f /dev/rmt/0cbn rew (rewind the drive) is sent, it goes via the /dev/rmt/ file for that tape drive.
Some scsi commands such as 'test unit ready' go via the /dev/sg/ file for the drive, as they cannot go via /dev/rmt.
To be honest, the finer details are irrelvant, it is how it works, there is nothing that can be done to change it, and providing the sg driver is configured correctly, it will work fine.
Martin
