Configuring Multipathing on Tape Drives

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Tape I/O multipathing is disabled by default on SPARC-based and x86-based systems. Tape I/O multipathing does not support load-balancing because only one path is used to send I/Os.

Ensure that the tape device is supported by Oracle Solaris I/O multipathing. If one of the following conditions are true, a drive will be enumerated under scsi_vhci.

Inquiry data of the drive has set any of the Target Port Group Support (TPGS) bits.
Inquiry data of the drive has set the Multi Port (MultiP) bit.
Internal VID and PID table for a specific fops module lists a inquiry Vendor Identification (VID) and Product Identification (PID) of the drive.

You can use the sg_inq command to retrieve the inquiry data of the drive.

The instructions to retrieve internal VID and PID table are as follows:

Enable scsi_vhci_f_tape in the scsi_vhci.conf file. For more information, see How to Configure Multipathing on Tape Drives.
Reboot the system.

Check for the internal vendor and product information.

Vendor:  EXAMPLE.Inc      
Product:  SAMPLE-4A3
--
Vendor:  EXAMPLE.Inc     
Product:  SAMPLE-4DT

Add the VID and PID pair to the scsi_vhci.conf file and specify the fops module known to the system. For example:
```
scsi-vhci-failover-override = "VENDOR1 ProductA", "f_tape";
```
For more information about how to set the property scsi-vhci-failover-override, see How to Add Third-Party Devices.

How to Configure Multipathing on Tape Drives

Become an administrator.
For more information, see Using Your Assigned Administrative Rights in Securing Users and Processes in Oracle Solaris 11.3.
Copy the file /kernel/drv/scsi_vhci.conf to /etc/driver/drv/scsi_vhci.conf.
Edit the /etc/driver/drv/scsi_vhci.conf file to configure multipathing.
- If the inquiry data of the drive has set any of the TPGS bits, uncomment the following line:
```
# "misc/scsi_vhci/scsi_vhci_f_tpgs_tape",
```
- If the inquiry data of the drive has set MultiP bit, uncomment the following line:
```
# "misc/scsi_vhci/scsi_vhci_f_tape",
```
  Note - Starting with Oracle Solaris 11, the configuration files are read from both /kernel/drv and /etc/driver/drv, and then they are merged. For more information, see the /kernel/drv/README.driver file. The configuration files in the /etc/driver/drv/ directory must contain the customized configuration.
  
  After you enable tape I/O multipathing, existing device nodes under /dev/rmt are no longer valid because they will point to devices that do not exist after the reboot. The tape I/O multipathing utilizes only one path for I/O at a time even though there are multiple paths to the tape device. The remaining paths are used for automatic failover.