Lustre 1.6 Operations Manual

13.4 Downgrading Lustre from 1.6.4 to 1.4.12
This section describes how to downgrade Lustre version 1.6.4 to version 1.4.12.
13.4.1 Downgrade Requirements
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The file system must have been upgraded from 1.4.x. In other words, a file system
created or reformatted under 1.6 cannot be downgraded.
Any new OSTs that were dynamically added to the file system will be unknown
in version 1.4.x. It is possible to add them back using lconf --write-conf, but
you must be careful to use the correct UUID of the new OSTs.
Downgrading an MDS that is also acting as an MGS prevents access to all other
file systems that the MGS serves.
13.4.2 Downgrading a File System
To downgrade a file system:
1. Shut down all clients.
2. Shut down all servers.
3. Install Lustre 1.4.x on the client and server nodes.
4. Restart the servers (OSTs, then MDT) and clients.
Caution – When you downgrade Lustre, all OST additions and parameter changes
made since the file system was upgraded are lost.
Chapter 13 Upgrading Lustre 13-11