Red Hat DEVICE-MAPPER MULTIPATH 5.2 Manual do Utilizador descarregar pdf (Página 10)

DotHill – Linux Device Mapper Multipath “How To” for Storage Revision 4

Multipath configurations require that you map each instance of a storage resource (partition) to

two different host channels on the SANnet controller. This is explained in detail in the SANnet II

200 FC and SATA Array Best Practices Manual (part number 83-00003263) available in the Dot

Hill Web site (www.dothill.com/support

6.2 Configuring DM-MP with the multipath.conf file

Initial configuration of DM-MP devices is done through entries in the configuration file

/etc/multipath.conf. The parameters in this file provide a variety of options for setting the

attributes and behavior of a multipath device including the I/O spreading policy, the path selector

algorithm, the polling interval for path status verification, and the program used by multipath to

obtain the WWID.

After making changes to the multipath.conf file you must restart the multipathd daemon for

the changes to take effect. Table 1 lists the important attributes appropriate for the SANnet and

R/Evo arrays along with their descriptions and possible values.

Table 1: Supported Multipath Attributes

Attribute Description Supported Values

path_grouping_policy

Determines how paths are assembled

into path groups.

• failover: one path per path

group

• multibus: all valid paths in one

path group

• group_by_serial: one path

group per detected controller

• group_by_prio: one path group

per path priority value

path_checker

Command that is used to determine

the status of a path.

• tur: SCSI TEST UNIT READ

command

• readsector0: READ sector 0 of

storage resource

getuid_callout

Command that is used to obtain the

WWID for the device

• scsi_id -g -u -s device

path_selector

Specifies the algorithm used for path

selection within a path group.

• round-robin 0

failback

Manages the path group failback

• manual

• immediate

• n (n>0); failback deferred for n

seconds

prio_callout

Executable to obtain a path weight for

a block device. Weights are summed

for each path group to determine the

next path group to use in case of path

failure

• none

• /sbin/mpath_prio_alua

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 29 30

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