[lustre-discuss] upgrading old lustre version (2.4.1)

[Riccardo Veraldi]

Hello,
I am planning to upgrade my MDS and OSS (several of them to Lustre 2.9.0
I would rather avoid that but my clients are all RHEL73 with 2.9.0
Lustre client.
Apparently the 2.9.0 client is working fine with the 2.4.1 server....
The question is, if I decide to upgrade how can I go from 2.4.1 to 2.9.0
on the servers ?
from which intermediate Lustre versions I have to go through ?
is there a procedure ?
Is there a remote possibility to lose data on the OSTs  during the
upgrade ??

thanks

Riccardo