Architecture - Interoperability 1.6 1.8 2.0

Note: The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.

Definitions

1.6	current b1_6 branch
1.6-fid	b1_6 branch with client support for b_new_cmd wire format. No cmd.
1.8	current b_new_cmd code without clustered metadata functionality, with features to transition from 1.6 to cmd storage.
1.8 limited mode	A 1.8 server mounted in limited mode is able to run on top of 1.6 storage, and interoperates with 1.6-fid clients.
1.8 full mode	Full mode is achieved through a mount option. It uses 1.8 b_new_cmd code. Server can handle mixed 1.6 and 1.8 storage and makes format changes to the file system that are not compatible with 1.8. No clustered metadata. No interoperability with 1.6 clients.
format upgrade	a background script that runs while a 1.8 server is running and upgrades all directory formats to cmd3 format.
2.0	cmd3 code with full interoperability with 1.8 and clustered metadata features.
limited protocol	minor discrepancies for 1.6 client - 1.8 server interaction compared with 1.6 -1.6 and 1.8-1.8 interaction.

b_new_cmd is also referred to as cmd3.

1.6-fid will be relased as 1.6.N for some N.

QAS Summary Table

Id	Quality	Summary
upgrade-srv	Feature	A server in a 1.6 cluster is upgraded to 1.8. It can mount a 1.6 file system and start in restricted mode.
restricted-mode-srv	Feature	An upgraded server continues to mount a server file system in restricted moded until a directive is given.
downgrade-srv	Feature	A server which only has been started in restricted mode is downgraded to a 1.6 server. The 1.6 server can start if only 1.6 clients are present in the cluster.
client-interop	Feature	A 1.6 client can interoperate with an upgraded server and 1.8 clients running in restricted mode.
client-upgrade	Feature	A cluster has upgraded all servers from 1.6 to 1.8. An upgrade of a client from 1.6 to 1.8 succeeds.