Multipath
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https://en.wikipedia.org/wiki/Linux_DM_Multipath https://linux.die.net/man/8/multipath
multipath -l
multipath -ll
multipath -ll DEVICE_NAME
multipath -t
-t
Display the currently used multipathd configuration
multipathd show config
- Ubuntu:
multipath-tools
package- Binaries:
multipath
multipathd
mpathpersist
- Binaries:
- RHEL:
device-mapper-multipath
package
Config files:
/etc/multipath.conf
[1]https://manpages.debian.org/unstable/multipath-tools/multipath.conf.5.en.html
/etc/multipath/wwids
- multipath -w 3600a09803831417a5a244f5665797a48
- wwid '3600a09803831417a5a244f5665797a48' removed
multipath -W successfully reset wwids
Contents
Configuration file: /etc/multipath.conf [2]
- System level defaults (defaults): User can override system level defaults.
- Blacklisted devices (blacklist): User specifies the list of devices that is not to be under the control of DM-MPIO.
- Blacklist exceptions (blacklist_exceptions): Specific devices to be treated as multipath devices even if listed in the blacklist.
- Storage controller specific settings (devices): User specified configuration settings will be applied to devices with specified "Vendor" and "Product" information.
- Device specific settings (multipaths): Fine tune the configuration settings for individual LUNs.
Default multipath.conf configuration
RHEL cat /etc/multipath.conf | grep -v "#" | grep . defaults { polling_interval 5 no_path_retry 4 user_friendly_names no flush_on_last_del yes fast_io_fail_tmo 5 dev_loss_tmo 30 max_fds 4096 } blacklist { protocol "(scsi:adt|scsi:sbp)" } devices { device { all_devs yes no_path_retry 4 } }
Routing policies implemented: failover, multibus and group_by_serial
- 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
- Varoqui, C. (2010.) The Linux multipath implementation. Retrieved from http://christophe.varoqui.free.fr/refbook.html
See also
- EMC
powerpath
kpartx
- Fibre Channel: SAN, HBA, LUN, WWN, WWPN, LIF,
rescan-scsi-bus.sh
- Block devices:
blkid
(UUID),lshw -class disk
,hwinfo --disk
,udevadm
,rescan-scsi-bus.sh
,LUN
,hdparm
,findfs
, Add a new disk lsblk
,pvscan
lspci
,lsscsi
,smartctl
,fdisk
,parted
,Kpartx
,pvdiplay
,pvs
,udisksctl
,/dev/sd, nvme list
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