Red Hat GNBD WITH GLOBAL FILE SYSTEM IN RHEL 4.5 Guide d'installation télécharger pdf (Page 27)

Configuration File Defaults

Attribute Description

polling_interval Specifies the interval between two path checks in seconds. The

default value is 5.

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

use for the next I/O operation. The default value is round-robin

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

The default value is failover.

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

unique path identifier. An absolute path is required.

The default value is /sbin/scsi_id -g -u -s /block/%n.

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 (Red Hat Enterprise Linux 5.5 and later),

emc_clariion, hp_sw, and directio. The default value is

readsector0.

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”.

rr_min_io Specifies the number of I/O requests to route to a path before

switching to the next path in the current path group. The default

value is 1000.

max_fds (Red Hat Enterprise Linux 5.2 and later) Sets the maximum

number of open file descriptors for the multipathd process.

In Red Hat Enterprise Linux 5.3, this option allows a value of

max, which sets the number of open file descriptors to the system

maximum.

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. The default value is

uniform.

failback Specifies path group failback.

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