Moving File Systems from a Single Path Device to a Multipath

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I am trying to work out how to move single path devices to multipath. the single path devices are all part of a volume group.
Our storage device is a Dell md3460 direct connected to a Dell PowerEdge server running Red Hat Enterprise Linux Server release 7.3 (Maipo).
The problem I am having is that it appears that the file system was original setup as single path. I would like to move these to multipath without breaking the volume group. Any help would be greatly appreciated.

Responses

Linux LVM doesn't care much about the PV device name. If the device name is different from what it was the last time the VG was activated, that is not a problem.

Normally, if the same PV is detected on multiple devices, LVM should prefer the dm-multipath device for that PV if one is available.

What you described usually happens if the VG was activated before the multipath subsystem was started. Does the volume group contain the root filesystem or any other essential OS filesystems you cannot unmount?

If not, then try this: Unmount the filesystems belonging to the problem VG.

Deactivate the VG: vgchange -an Name_of_your_VG

Activate the multipathing if it isn't already active: mpathconf --enable --find_multipaths y --with_multipathd y

Rescan for multipath devices: multipath -v2

See if LVM now detects the PV(s) of that VG through multipath devices: pvs

If necessary, force LVM to scan again: vgscan; pvs

Activate the volume group again: vgchange -ay Name_of_your_VG

Mount the filesystem(s).

Recreate your initrd to make it aware of the requirement to start multipath before activating LVM volume groups.

If your volume group includes the root filesystem or other filesystems you cannot unmount while the system is running, see chapter 5.3 of this document: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-7-DM_Multipath-en-US.pdf

Good input from Matti, but I was thinking about how were the paths become multipath? Was this because, you added a secondary controller on the storage device? Anyways, I feel it would be better if you could provide more details on the same... How were the paths made multipath? Also, details about your current logical volumes, pvs, vgs,...lsblk, and mount details etc..

Thank you Matti

I can confirm that it works as expected thanks for your assistance.

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