I have an older redhat (5) server that needs to have 9 array filesystems moved to a new array. I'm seeking some assistance on the best way of doing this and how the process works.
The data is being copied directly as an array level copy. I have been given the 9 LUNids (WWN) from the existing server and I see them in the output of multipath -ll. I also have the LUNids on the new storage that correspond to the old. I am unsure how to migrate to the new storage. I don't fully understand the role of LVM commands like pvscan. I think the procedure is going to be to quiesce the array filesystems and unmount them and remove from /etc/fstab so they don't try to be mounted on boot. Then shutdown server and connect the new array LUNids, then boot. At this stage I expect to see the new LUNids from multipath -ll. Is this correct? And as I've not specified any custom device naming I will also see device names of the form mpathX for each? I know that each PV has a UUID, as does a VG and LV. Is that the key information that allows LVM to reconstruct each PV and consequently the volume groups and logical volumes such that it all contains the same data? That is, the PV of /dev/mapper/mpath24 from one of the new LUNid disks will be the same data because its been identified by the UUID that is on that disk?
Will this just work? After the reboot and multipath has discovered and enumerated the paths and devices (and updated /etc/multipath/bindings) will LVM simply start, automatically interrogate the disks and essentially, Just Work? So I can go ahead and mount the filesystems just as before?
If not what steps do I need to take? Do I need to run pv/vg/lv scan? It would be helpful to know what happens when multipath starts up, and what happens when LVM starts.
Lastly, is it possible to avoid a reboot, or is it safest to do that for orderliness of the processes? If I could do this without reboot what steps would I need to take after umounting filesystems and attaching the new LUNids? Is there are sequence of multipath and subsequent LVM commands that would do the same thing as a reboot process? and any additional steps I need in either case?