Configuring tape libraries on a SAN for Netvault using persistent bindings (4042446)

Configuring tape libraries on a SAN for Netvault using persistent bindings

This article explains the general configuration rules to guide you when you are adding tape libraries to NetVault when the library is attached to a Fibre Channel SAN.

When configuring tape libraries on a SAN and your intention is to use NetVault as the controlling software, it is recommended that persistent bindings are used. These are also known as SCSI mappings, persistent reservations, naming etc.

They should be used because a SAN can be a changing environment, and this can also cause SCSI addresses that have been assigned to a fibre device or devices attached through a fibre bridge or switch to change.
This causes problems with NetVault as when a device is added in the NetVault Device Manager, it is assigned a SCSI address (i,.e. Bus, Channel, Target, LUN) and node name, and if the address of the library changes, NetVault is unable to communicate with the library.

Persistent binding or naming creates a fixed SCSI address to physical device relationship, which does not change as devices are added or removed on the SAN. This works differently for different Host Bus Adapters, and the most common way of doing this is for the HBA to map the Fibre Channel device addresses (World Wide Names, WWNs, WWID) or a loop ID to SCSI addresses. This ensures that there is no impact on NetVault as the SAN changes.

For example if you are using QLogic FC cards, then you can use their persistent bindings managing software called SANsurfer.
Further information is on the following link:

http://filedownloads.qlogic.com/files/ms/49541/ReadmeSANsurferFCmgr.htm

It is best to allocate persistent bindings when server and fibre devices are attached to a separate switch or when using zoning, having server and devices together in their own zone. If you are using a Smart Client, it should be part of the same zone, and its SCSI IDs should be tied down to the same ones the server is using.

In general, tape libraries and drives do not support multipathing. Drives are streaming devices and failover/load-balancing would interrupt the streams. Ensure that multipathing is not enabled for these devices.

Hardware vendors also recommend that tape libraries/drives are not used on the same switch/in the same zone that has disk devices attached. The best way of achieving this is by using separate HBA's for each, but at the very least, different zones should be used.