Hi Jake,
On 9/12/22 11:06, Jake Anderson wrote:
I must confess that I have little knowledge about Multipathing but still
based on my research below is what I understood
My storage team has given a LUN ID of 500g
So as per df -TH
I see
/dev/mapper/bradvg2-u03_lv is mounted on /u03
So similarly I have to create another mount point with /u04
So If my understanding is correct I need to run multipath -d to scan the
newly LUN added.
It depends on whether you are using zfcp automatic LUN scan or not.
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=20
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=21
https://www.ibm.com/docs/en/linux-on-systems?topic=devices-configure
If so (and the storage already mapped the volume to the host, of course),
you only need to trigger a LUN scan for Linux to dynamically find the new paths
to the volume. That can be "rescan-scsi-bus.sh -a" or more directly (I
typically prefer this):
https://www.ibm.com/docs/en/linux-on-systems?topic=scanning-trigger-lun-scan
Then do echo the new LUN ID to the device driver
The apply changes to /etc/zipl.conf
If you don't use zfcp automatic LUN scan, then you have to explicitly configure
multiple paths to the new volume presistently in Linux.
The volume usage sounds like it's a data volume, i.e. not part of the root file
system, so we don't touch /etc/zipl.conf, but only /etc/zfcp.conf.
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=23
=>
https://www.ibm.com/docs/en/linux-on-systems?topic=devices-manually-configured-fcp-luns
=>
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/performing_a_standard_rhel_8_installation/configuring-a-linux-instance-on-ibm-z_installing-rhel#fcp-luns-that-are-not-part-of-the-root-file-system_configuring-a-linux-instance-on-ibm-z
In either case, a running multipathd ensures the new LUN paths are
automatically assembled into a new multipath device representing your new
volume.
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=15
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=16
You can then prepare the new volume as you did for your already existing LVM
PhysicalVolume(s) within VolumeGroup bradvg2, so likely something like pvcreate
on the new multipath device (or on a partition thereof).
LVM in recent Linux distributions automatically ignores individual single paths
to a volume and makes use of multipath devices instead when scanning
PhysicalVolumes.
Older distributions might need an explicit LVM filter to accomplish this.
https://public.dhe.ibm.com/software/dw/linux390/lvc/zFCP_Best_Practices-BB-Webcast_201805.pdf#page=46
FYI: In case you happen to run RHEL 9.x, you would instead have to deal with
the new LVM device filter (different from above-mentioned LVM filter):
The RHEL installer "anaconda" disables auto PV scan by populating
/etc/lvm/devices/system.devices, so the user needs to add new PVs by means of
"lvmdevices --adddev ...".
https://bugzilla.redhat.com/show_bug.cgi?id=2002550#c0
https://sourceware.org/git/?p=lvm2.git;a=commit;h=83fe6e720f42711ff183a66909b690b726702f58
Then perform lv addition
Is my understanding correct? Could someone please be kind to share the
steps of adding the newly added LUN ID to an existing LV ?
Your above steps with a new separate mount point, do not sound like you would
add the new physical volume to an existing LVM VolumeGroup, which would be
another possibility.
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/configuring_and_managing_logical_volumes/index#modifying-the-size-of-a-logical-volume_configuring-and-managing-logical-volumes
--
Mit freundlichen Gruessen / Kind regards
Steffen Maier
Linux on IBM Z and LinuxONE
https://www.ibm.com/privacy/us/en/
IBM Deutschland Research & Development GmbH
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Geschaeftsfuehrung: David Faller
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