Red Hat ENTERPRISE LINUX 5 - LOGICAL VOLUME MANAGER ADMINISTRATION Manual page 99

start
starting block in virtual device
length
length of this segment
#features
The number of multipath features, followed by those features. If this parameter is zero, then
there is no feature parameter and the next device mapping parameter is #handlerargs.
Currently there is one supported multipath feature, queue_if_no_path. This indicates that this
multipathed device is currently set to queue I/O operations if there is no path available.
For example, if the no_path_retry option in the multipath.conf file has been set to queue I/
O operations only until all paths have been marked as failed after a set number of attempts have
been made to use the paths, the mapping would appear as follows until all the path checkers have
failed the specified number of checks.
0 71014400 multipath 1 queue_if_no_path 0 2 1 round-robin 0 2 1 66:128 \
1000 65:64 1000 round-robin 0 2 1 8:0 1000 67:192 1000
After all the path checkers have failed the specified number of checks, the mapping would appear
as follows.
0 71014400 multipath 0 0 2 1 round-robin 0 2 1 66:128 1000 65:64 1000 \
round-robin 0 2 1 8:0 1000 67:192 1000
#handlerargs
The number of hardware handler arguments, followed by those arguments. A hardware handler
specifies a module that will be used to perform hardware-specific actions when switching path
groups or handling I/O errors. If this is set to 0, then the next parameter is #pathgroups.
#pathgroups
The number of path groups. A path group is the set of paths over which a multipathed device will
load balance. There is one set of pathgroupargs parameters for each path group.
pathgroup
The next path group to try.
pathgroupsargs
Each path group consists of the following arguments:
pathselector #selectorargs #paths #pathargs device1 ioreqs1 ... deviceN
ioreqsN
There is one set of path arguments for each path in the path group.
pathselector
Specifies the algorithm in use to determine what path in this path group to use for the next I/O
operation.
The multipath Mapping Target
87