[lustre-discuss] Adding a new NID

[Vicker, Darby (JSC-EG311)]

Hello everyone,

We have an existing LFS that is dual-homed on ethernet (mainly for our workstations) and IB (for the computational cluster), ZFS backend for the MDT and OST's.  We just got a new computational cluster and need to add another IB NID.  The procedure for doing this is straight forward (14.5 in the admin manual) and amounts to:

Unmount the clients
Unmount the MDT
Unmount all OSTs
mount -t lustre MDT partition -o nosvc mount_point
lctl replace_nids devicename nid1[,nid2,nid3 ...]

We haven't had to update a NID in a while so I was happy to see you can do this with "lctl replace_nids" instead of "tunsfs.lustre --writeconf".

I know this is dangerous, but we will sometime make minor changes to the servers by unmounting lustre on the servers (but leaving the clients up), make the changes, then remount the servers.  If we are confident we can do this quickly, the clients recover just fine.

While this isn't such a minor change, I'm a little tempted to do that in this case since nothing will really change for the existing clients – they don't need the new NID.  Am I asking for trouble here or do you think I can get away with this?  I'm not too concerned about the possibility of it taking too long and getting the existing clients evicted.   I'm (obviously) more concerned about doing something that would lead to corrupting the FS.  I should probably schedule an outage and do this right but... :)

Darby
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