IBM TS2340 User Guide - Page 127
Querying Primary and Alternate Path Configuration, Disable and Enable Primary and Alternate Paths
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Linux Device Driver (lin_tape) changer. The other logical medium changers that lin_tape attached for the same medium changer are configured as alternate paths. The device driver supports up to 16 physical paths for a single device. The primary and alternate path information can be obtained by the following command: v cat /proc/scsi/IBMchanger The following is an example of a /proc/scsi/IBMchanger file: v lin_tape version: 3.0.3 v lin_tape major number: 253 Attached Changer Devices: Number 0 1 2 Model 03584L22 03584L22 03584L22 SN IBM1234567 IBM1234567 IBM1234567 HBA qla2xxx qla2xxx qla2xxx FO Path Primary Alternate Alternate The labeling of a logical device as either a primary or alternate path is for information only, in order to: v Be able to identify the actual number of physical devices configured on the system and a specific logical device associated with them. There is only one logical device labeled as the primary path for each physical device. However, there can be multiple logical devices labeled as an alternate path for the same devices. v Provide information about which logical devices configured on the system have path failover support enabled. Querying Primary and Alternate Path Configuration You can display the primary and alternate path configuration for all devices by reading the /proc/scsi/IBMchanger file, as explained in section "Primary and Alternate Paths" on page 108. Note: Display the primary and alternate path configuration for any device using tape diagnostic and utility functions, refer to Chapter 10, "IBM Tape Diagnostic Tool (ITDT)," on page 259 or "Linux System - Tape Utility Program (IBMtapeutil)" on page 385. Disable and Enable Primary and Alternate Paths Once you load the lin_tape device driver with the alternate_pathing parameter to be ON, by default, all the available paths for a physical device are enabled. If it is necessary to disable a path and not perform path fail over (for example due to maintenance), run commands to disable and then later enable the primary and alternate paths. The commands to enable and disable primary and alternate paths are tape diagnostic and utility functions. Note: See Chapter 10, "IBM Tape Diagnostic Tool (ITDT)," on page 259 or "Linux System - Tape Utility Program (IBMtapeutil)" on page 385 Chapter 5. Linux Tape and Medium Changer Device Driver 109