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Invoking persistent name binding

Is there any way to invoke persistent name binding other than through the driver software offered by the HBA manufactures? None that I have contacted so far allow for this option in Novell.

I have a SAN implementation that includes Win2K servers, Novell servers, a Fibre Switch and tape libraries with internal Fibre to SCSI bridges. With multiple libraries, we are loosing the assigned SCSI ID that is recorded into the backup software when there is a power loss. For instance, if there is a power outage during the backup window, the servers reboot, the switch and libraries reboot, but the IDs that have been recorded into the backup software are now incorrect and the backup does not work until a scan of the new SCSI bus IDs is done on the SAN and then entered into the backup software.

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Glad you asked. Yup, this is an easy one. You mentioned your tape libraries are connected via SCSI bridges. This is where you need to do your changes. To allow Fibre Channel and SCSI devices to address each other, the data router (bridge) creates a table that maps device identifiers between Fibre Channel and SCSI. During configuration, the mapping method can be specified.

I don't know how many times I have encountered this issue. What you need to do is have your SAN vendor come in and connect a laptop to the management port of the SCSI bridges connecting the tape Libraries to the SAN. There a few modes these bridges use to collect SCSI target IDs for the drives in the library, including the robot. The default method is "automatic" mode, which arbitrarily assigns SCSI IDs to the tapes in the library. The other method is "persistent" or "assigned." This is what you need to change. You need to map which SCSI ID gets mapped to which tape drive.

If it's a Crossroads router like the 4x50 (IBM uses chaparral, which works the same), break out the manual and read it first. Now go to the "perform configuration" screen, and select "SCSI to Fibre Channel Mapping Configuration". There is an "automatic discovery option" in the Fibre Channel to SCSI mapping menu, this is set to "Auto Addressing" by default. What happens in automatic mode is the device randomly assigns SCSI IDs to the tape heads and the robot any time the device is rebooted. As you have found out, this really sucks. The setup also lets you set a persistent ID for each device in the library. You can connect the robot to SCSI BUS 0, along with the first tape head. Set the robot to ID 0, and the first tape head to 1 on the first bus. On the next bus, set the next tape ID to 0, and the next to 1, and so on until you use up all the buses. You could use progressing ID's 2,3,4 and so on for the next tape devices, but some tape backup software don't like to see anything above ID 3 for some reason. (I have yet to figure this out.) As long as you are on different busses, using the same SCSI ID should not matter. Contact your data router vendor for detailed information on this if the storage vendor can't help.

Once everything is set up persistent, reboots will keep exporting to the fabric the same ID for the devices every time. Take a look in control panel in NT under TAPES and look at the tape properties to make sure the SCSI IDs match against the IDs you set up in the library.

Chris

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This was first published in January 2002

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