Primary and alternative paths
When the lin_tape device driver is loaded into kernel memory with path failover support enabled, the first logic device that lin_tape sees always becomes the primary path. The other logical devices that lin_tape sees are configured as the alternative paths. The device driver supports up to 16 physical paths for a single device.
lin_tape version: 3.0.3 lin_tape major number: 253
The labeling of a logical device as either a primary or alternative path is for information only and is used for following purpose:
- Identify the actual number of physical devices that are configured on the system and a specific logical device that is associated with them. Only one logical device is labeled the primary path for each physical device. However, many (multiple) logical devices can be labeled as an alternative path for the same device.
- Provide information about which logical devices configured on the system have path failover support enabled.
The numbers listed in Table 1 are the ones used for IBMchanger special files at /dev directory (see Special files for the tape device). An attempt to open a device file name not listed at /dev directory will fail. Per file systems handling and due to path removal, usually a device file name is deleted after a device closes or before a device opens. Using Persistent naming support will maintain device file names listed under ls -l /dev/lin_tape/by-id/.
Only one st and one sg device file name per device can use all the paths for that device.
pfo9 sg=/dev/sg9 st=/dev/st0 sf=yes fo=no wwnn=500507630f04be07 type=tape 2:0:1:0 up last - wwpn=500507630f44be07 3:0:1:0 - - - -