Red Hat GNBD WITH GLOBAL FILE SYSTEM IN RHEL 4.5 Guida di Installazione Scaricare il pdf (Pagina 32)

Chapter 4. The DM-Multipath Configuration File

Attribute Description

product Specifies the product name of the storage device to which the

device attributes apply, for example HSV110 (C)COMPAQ.

path_grouping_policy Specifies the default path grouping policy to apply to unspecified

multipaths. Possible values include:

failover = 1 path per priority group

multibus = all valid paths in 1 priority group

group_by_serial = 1 priority group per detected serial number

group_by_prio = 1 priority group per path priority value

group_by_node_name = 1 priority group per target node name

getuid_callout Specifies the default program and arguments to call out to obtain a

unique path identifier. An absolute path is required.

prio_callout Specifies the default program and arguments to call out to obtain

a path weight. Weights are summed for each path group to

determine the next path group to use in case of failure. "none" is a

valid value.

path_checker Specifies the default method used to determine the state of

the paths. Possible values include readsector0, rdac, tur,

cciss_tur, hp_tur, emc_clariion, hp_sw, and directio.

path_selector Specifies the default algorithm to use in determining what path to

use for the next I/O operation.

features The extra features of multipath devices. The only existing

feature is queue_if_no_path, which is the same as setting

no_path_retry to queue. For information on issues that may

arise when using this feature, see Section 5.4, “Issues with

queue_if_no_path feature”.

hardware_handler Specifies a module that will be used to perform hardware specific

actions when switching path groups or handling I/O errors.

Possible values include 0, 1 emc, and 1 rdac. The default value

is 0.

rr_weight If set to priorities, then instead of sending rr_min_io

requests to a path before calling selector to choose the

next path, the number of requests to send is determined by

rr_min_io times the path's priority, as determined by the

prio_callout program. Currently, there are priority callouts only

for devices that use the group_by_prio path grouping policy,

which means that all the paths in a path group will always have the

same priority.

If set to uniform, all path weights are equal.

no_path_retry A numeric value for this attribute specifies the number of times

the system should attempt to use a failed path before disabling

queueing.

A value of fail indicates immediate failure, without queuing.

A value of queue indicates that queuing should not stop until the

path is fixed.

failback Specifies path group failback.

A value of 0 or immediate specifies that as soon as there is a

path group with a higher priority than the current path group the

system switches to that path group.

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