[lustre-discuss] MGS+MDT migration to a new storage using LVM tools

[David Cohen]

Hi,
We have a combined MGS+MDT and I'm looking for a migration to new storage
with a minimal disruption to the running jobs on the cluster.

Can anyone find problems in the scenario below and/or suggest another
solution?
I would appreciate also "no problems" replies to reassure the scenario
before I proceed.

Current configuration:
The mdt is a logical volume in a lustre_pool VG on a /dev/mapper/MDT0001 PV

Migration plan:
Add /dev/mapper/MDT0002 new disk (multipath)
extend the VG:
pvcreate /dev/mapper/MDT0002
vgextend  lustre_pool /dev/mapper/MDT0002
mirror the mdt to the new disk:
lvconvert -m 1 /dev/lustre_pool/TECH_MDT /dev/mapper/MDT0002
wait the mirrored disk to sync:
lvs -o+devices
when it's fully synced unmount the MDT, remove the old disk from the mirror:
lvconvert -m 0 /dev/lustre_pool/TECH_MDT /dev/mapper/MDT0001
and remove the old disk from the pool:
vgreduce lustre_pool /dev/mapper/MDT0001
pvremove /dev/mapper/MDT0001
remount the MDT and let the clients few minutes to recover the connection.

Thanks,
David
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