Steps to disconnect external SCSI tape drives

[rico_cebiche]

Hi,

What steps I should follow to disconnect external scsi tape drives ?
Do I need to reboot the servers before disconnecting the external drives ?
Can this procedure be done with the OS up and running ?
What commands should I use to update OS configuration, so it won't keep old reference to old external drives ?

[A. Clay Stephenson · Accepted solution]

The safe way is to shutdown the server, power off the tape drive, and then disconnect the cable and move the terminator to the last physical device on the bus. This is the only supported and reccomended procedure for removing tape drives --- although hot-plug tape modules can be removed and replaced "on the fly".

Now, can you do it another way? Yes, almost always. Generally, it's very difficult to shutdown a production system for a tape drive replacement. If your tape drives is on a dedicated bus --- or at least on a SCSI bus with only inactive devices such as other tape drives then I routinely replace them while the machine is up and running --- and I've never had a hang on an HP-UX box --- but this still doesn't meran that this is a reccomended approach.

You can use the rmsf command to remove unwanted device nodes. Man rmsf for details.

[Rick Garland]

The system really should be down for connecting/disconnecting the SCSI tape drives. If there is traffic across the bus when you pull the connection it could cause more problems and force you to reboot.

The safest way to to shutdown the system, connect/disconnect the SCSI tape drive, then power on.

[rico_cebiche]

It is clear that I should shutdown the server to disconnect external SCSI devices.
What about the clean up of the drivers or devices reference in OS, is ther a command to do this ?

[Torsten.]

Hi,

as mentioned before, do a "rmsf" to remove the device files prior to unconnect them.
see "man rmsf"

[rico_cebiche]

What could happen if we follow the next steps to disconnect external tape drive :
1. Shutdown server
2. Power down external tape drive.
3. Disconnect SCSI cable from tape drive.
4. Move SCSI terminator to last position in bus.
5. Start server.
Do we need to perform rmsf command ? Will the OS cleanup special files by itself ? Any problems in the secuence of steps ?

[Patrick Wallek]

If you do the steps you mention, the OS itself will remove the entries from the device list (they won't show up in ioscan) but you may still be left with device files in /dev/rmt. If so, you can still use rmsf to remove those.

[rico_cebiche]

rmsf used before shutdown. SCSI device disconnected while server down. Boot without problems.