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3.2. Ignoring Local Disks when Generating Multipath Devices
Some machines have local SCSI cards for their internal disks. DM Multipath is not recommended for these devices. If you set the
find_multipaths configuration parameter to yes, you should not have to blacklist these devices. For information on the find_multipaths configuration parameter, see Section 4.3, “Configuration File Defaults”.
If you do not set the
find_multipaths configuration parameter to yes, can use the following procedure to modify the multipath configuration file to ignore the local disks when configuring multipath.
- Determine which disks are the internal disks and mark them as the ones to blacklist.In this example,
/dev/sdais the internal disk. Note that as originally configured in the default multipath configuration file, executing themultipath -v2command shows the local disk,/dev/sda, in the multipath map.This examples specifies the-doption of themultipathcommand to indicate that this is a dry run that will not create the multipath devices. For further information on themultipathcommand output, see Section 5.7, “Multipath Command Output”.#
multipath -v2 -d: SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1 undef WINSYS,SF2372 size=33 GB features="0" hwhandler="0" wp=undef `-+- policy='round-robin 0' prio=1 status=undef |- 0:0:0:0 sda 8:0 [--------- : 3600a0b80001327d80000006d43621677 undef WINSYS,SF2372 size=12G features='0' hwhandler='0' wp=undef `-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:0 sdb 8:16 undef ready running `- 3:0:0:0 sdf 8:80 undef ready running : 3600a0b80001327510000009a436215ec undef WINSYS,SF2372 size=12G features='0' hwhandler='0' wp=undef `-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:1 sdc 8:32 undef ready running `- 3:0:0:1 sdg 8:96 undef ready running : 3600a0b80001327d800000070436216b3 undef WINSYS,SF2372 size=12G features='0' hwhandler='0' wp=undef `-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:2 sdd 8:48 undef ready running `- 3:0:0:2 sdg 8:112 undef ready running : 3600a0b80001327510000009b4362163e undef WINSYS,SF2372 size=12G features='0' hwhandler='0' wp=undef `-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:3 sdd 8:64 undef ready running `- 3:0:0:3 sdg 8:128 undef ready running - In order to prevent the device mapper from mapping
/dev/sdain its multipath maps, edit the blacklist section of the/etc/multipath.conffile to include this device. Although you could blacklist thesdadevice using adevnodetype, that would not be a safe procedure since/dev/sdais not guaranteed to be the same on reboot. To blacklist individual devices, you can blacklist using the WWID of that device.Note that in the output to themultipath -v2command, the WWID of the/dev/sdadevice is SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1. To blacklist this device, include the following in the/etc/multipath.conffile.blacklist { wwid SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1 } - After you have updated the
/etc/multipath.conffile, you must manually tell themultipathddaemon to reload the file. The following command reloads the updated/etc/multipath.conffile.#
systemctl reload multipathd.service
