Difference between revisions of "Multipath"

Latest revision as of 09:36, 20 September 2020

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

mpathconf
- mpathconf --enable --with_multipathd y
multipath -l (show the current multipath topology from information fetched in sysfs and the device mapper)
multipath -ll
- multipath -ll DEVICE_NAME

multipath -v2 or multipath -v3
multipath -t

-t Display the currently used multipathd configuration

multipathd show config

Ubuntu: multipath-tools package
- Binaries: multipath multipathd mpathpersist
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

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

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.

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]

Varoqui, C. (2010.) The Linux multipath implementation. Retrieved from http://christophe.varoqui.free.fr/refbook.html
Changelog: https://git.opensvc.com/?p=multipath-tools/.git;a=log

Related terms[edit]

blkid multipath -f multipath -w pvcreate
multipath-tools Ubuntu package
Hitachi Dynamic Link Manager (HDLM)

Activities[edit]

Review no_path_retry configuration options in multipath.conf to avoid pvs to hang : https://www.suse.com/support/kb/doc/?id=7022310
Multipath: remove multipath device unpresented to host: multipath -f
Review multipath-tools source code: https://git.opensvc.com/gitweb.cgi?p=multipath-tools%2F.git
Map some LUN to your system with multipath uninstalled and verify no dm devices are created. Install multipath and check again.

See also[edit]

EMC powerpath
kpartx
HBA, rescan-scsi-bus.sh, /sys/class/fc_host/
Fibre Channel: HBA, multipath-tools, multipath, multipath -ll, /etc/multipath.conf multipathd rescan-scsi-bus.sh powermt Device mapper dmsetup ls,
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
LVM: LVM errors LVM scan commands lkvmetad, Add a new disk

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, lvreduce, lvrename

VG: vgdisplay,vgcreate,vgremove, vgextend, vgreduce, vgscan, vgchange, vgrename, vgcfgbackup, vgcfgrestore, vgimportclone, vgck

Check commands: pvck vgck

↑ https://www.thegeekdiary.com/understanding-the-dm-multipath-configuration-file-etc-multipath-conf/

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

[1]

[2]

@@ Line 1: / Line 1: @@
 https://en.wikipedia.org/wiki/Linux_DM_Multipath
+* https://linux.die.net/man/5/multipath.conf
+* https://linux.die.net/man/8/multipath
+* https://linux.die.net/man/8/multipathd
-* <code>multipath -l</code>
+* <code>mpathconf</code>
+** <code>mpathconf --enable --with_multipathd y</code>
+* <code>multipath -l</code> (show the current multipath topology from information fetched in [[sysfs]] and the [[device mapper]])
+* <code>[[multipath -ll]]</code>
+** <code>multipath -ll DEVICE_NAME</code>
+* <code>[[multipath -v2]]</code> or  <code>[[multipath -v3]]</code>
 * <code>multipath -t</code>
-:<code>-t</code> Display the currently used multipathd configuration
+:<code>-t</code> Display the currently used [[multipathd]] configuration
-* <code>multipathd show config</code>
+* <code>[[multipathd]] show config</code>
 * [[Ubuntu]]: <code>multipath-tools</code> package
-** Binaries: <code>multipath</code> <code>multipathd</code> <code>mpathpersist</code>
+** Binaries: <code>multipath</code> <code>[[multipathd]]</code> <code>[[mpathpersist]]</code>
 * [[RHEL]]: <code>device-mapper-multipath</code> package
 Config files:
-* <code>/etc/multipath.conf</code><ref>https://www.thegeekdiary.com/understanding-the-dm-multipath-configuration-file-etc-multipath-conf/</ref><code>https://manpages.debian.org/unstable/multipath-tools/multipath.conf.5.en.html</code>
+* <code>/etc/[[multipath.conf]]</code><ref>https://www.thegeekdiary.com/understanding-the-dm-multipath-configuration-file-etc-multipath-conf/</ref><code>https://manpages.debian.org/unstable/multipath-tools/multipath.conf.5.en.html</code>
-* <code>/etc/multipath/wwids</code>
+* <code>/etc/multipath/[[wwids]]</code>
-== Configuration file: /etc/multipath.conf <ref>https://en.wikipedia.org/wiki/Linux_DM_Multipath</ref>==
+== Configuration file: /etc/[[multipath.conf]] <ref>https://en.wikipedia.org/wiki/Linux_DM_Multipath</ref>==
 # 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.
@@ Line 22: / Line 33: @@
 # Device specific settings (''multipaths''): Fine tune the configuration settings for individual LUNs.
+== Routing policies implemented: failover, multibus and group_by_serial ==
+* failover : 1 path per priority group. IO thus get routed to one path only.
-== Default multipath.conf configuration ==
+* multibus : 1 priority group containing all paths to the LU. Brings the maximum spreading, but assumes that all paths are excitable without penalty.
-<pre>
+* 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.
-RHEL
+To modify a policy for device [[major]] 8 and [[minor]]:
-cat /etc/multipath.conf | grep -v "#" | grep .
+* <code>multipath -p multibus -D 8 0</code>
-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
-    }
-}
-</pre>
 == Readings ==
 * Varoqui, C. (2010.) The Linux multipath implementation. Retrieved from http://christophe.varoqui.free.fr/refbook.html
+* Changelog: https://git.opensvc.com/?p=multipath-tools/.git;a=log
+== Related terms ==
+* <code>[[blkid]]</code> <code>[[multipath -f]]</code> <code>[[multipath -w]]</code> <code>[[pvcreate]]</code>
+* <code>[[multipath-tools]]</code> Ubuntu package
+* [[Hitachi Dynamic Link Manager (HDLM)]]
+== Activities ==
+* Review <code>no_path_retry</code> configuration options in [[multipath.conf]] to avoid [[pvs]] to hang : https://www.suse.com/support/kb/doc/?id=7022310
+* [[Multipath: remove multipath device unpresented to host]]: <code>multipath -f</code>
+* Review [[multipath-tools]] source code: https://git.opensvc.com/gitweb.cgi?p=multipath-tools%2F.git
+* Map some [[LUN]] to your system with multipath uninstalled and verify no [[dm]] devices are created. Install multipath and check again.
 == See also ==
-* EMC <code>powerpath</code>
+* [[EMC]] <code>[[powerpath]]</code>
-* {{Fibre Channel}}
+* <code>[[kpartx]]</code>
+* {{HBA}}
+* {{Linux Fibre Channel}}
+* {{Linux block devices}}
+* {{lvm commands}}
 [[Category:Linux commands]]

Difference between revisions of "Multipath"

Latest revision as of 09:36, 20 September 2020

Contents

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

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

Readings[edit]

Related terms[edit]

Activities[edit]

See also[edit]

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Difference between revisions of "Multipath"

Latest revision as of 09:36, 20 September 2020

Contents

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

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

Readings[edit]

Related terms[edit]

Activities[edit]

See also[edit]

Navigation menu

Search

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