About Control Paths

A control path is the connection between a partition and host application. The control path connection is made through a designated tape drive or through a Fibre Channel (FC) I/O blade.

Only one tape drive can be selected as the control path per partition. In the event that the tape drive control path connection to the host application fails, you can manually select a different control path tape drive for the partition (see Modifying Control Paths). If I/O blades are installed in the library, you can configure host port failover (see About FC Host Port Failover).

When you create a partition, the library automatically assigns control paths as follows:

If the library contains:

And the partition contains:

Then the default control path for the partition is:

If you want to change the control path, note the following:

No FC I/O blades

Any combination of tape drive interface types (FC, SAS, or SCSI)

The first tape drive assigned to the partition

You must select a tape drive as the control path.

One or more FC I/O blades

At least one FC tape drive

The FC I/O blade

It is recommended that you allow the FC I/O blade to be the control path for the partition.

(You can select a tape drive as control path if the tape drive is not connected to an FC I/O blade; however, your host will end up seeing multiple medium changers. In addition, using the FC I/O blade as the control path allows you to utilize the LUN mapping and host port failover features.)

One or more FC I/O blades

No FC tape drives

The first tape drive assigned to the partition

You must select a tape drive as the control path.

You can change the control path tape drive at any time by selecting Setup > Control Path from either the operator panel or the web client.

CAUTION: Do not select an FC tape drive as control path if it is connected to an FC I/O blade. The control path will be filtered out by the I/O blade and will not be visible to the host.

NOTE: If you have more than one FC I/O blade in the library, each FC I/O blade will present each partition — that does not have a tape drive as the control path — as a target device to the host. Thus the host may see the same partition multiple times. To minimize confusion, you should configure host mapping so that each host sees each device only once. See About FC Host Mapping.

See also: