Multipath

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https://en.wikipedia.org/wiki/Linux_DM_Multipath


  • mpathconf
    • mpathconf --enable --with_multipathd y
  • multipath -l
  • multipath -ll
    • multipath -ll DEVICE_NAME
-t Display the currently used multipathd configuration

Config files:

Configuration file: /etc/multipath.conf [2][edit]

  1. System level defaults (defaults): User can override system level defaults.
  2. Blacklisted devices (blacklist): User specifies the list of devices that is not to be under the control of DM-MPIO.
  3. Blacklist exceptions (blacklist_exceptions): Specific devices to be treated as multipath devices even if listed in the blacklist.
  4. Storage controller specific settings (devices): User specified configuration settings will be applied to devices with specified "Vendor" and "Product" information.
  5. Device specific settings (multipaths): Fine tune the configuration settings for individual LUNs.

Routing policies implemented: failover, multibus and group_by_serial[edit]

  • failover : 1 path per priority group. IO thus get routed to one path only.
  • multibus : 1 priority group containing all paths to the LU. Brings the maximum spreading, but assumes that all paths are excitable without penalty.
  • group_by_serial : 1 priority group per storage controller (serial), paths through one controller are assigned to the associated PG. This policy applies to controllers that impose a latency penalty on LU management hand-over between a pair of redundant controllers.

To modify a policy for device major 8 and minor:

  • multipath -p multibus -D 8 0

Readings[edit]

Related commands[edit]

Activities[edit]

See also[edit]

scan: pvscan vgscan
LVM: lvs lvmscan lvm fullreport lvmreport lvmconfig lvmdump lvmcheck lvm dumpconfig
Scan: pvs vgs lvs pvscan vgscan
PV: pvcreate pvremove pvscan pvremove pvscan pvs pvchange pvck pvdisplay pvresize
LV: lvdisplay lvcreate lvremove, lvresize, lvextend, lvrename, lvreduce
VG: vgdisplay,vgcreate, vgreduce,vgremove, vgextend, vgscan, vgchange, vgrename, vgcfgbackup, vgcfgrestore, vgimportclone, vgck
Check commands: pvck vgck
  1. https://www.thegeekdiary.com/understanding-the-dm-multipath-configuration-file-etc-multipath-conf/
  2. https://en.wikipedia.org/wiki/Linux_DM_Multipath