[lustre-discuss] Version interoperability

[Andrew Elwell]

Hi folks,

We're faced with a (short term measured in months, not years
thankfully) seriously large gap in versions between our existing
clients (2.7.5) and new hardware clients (2.15.0) that will be
mounting the same file system.

It's currently on 2.10.8-ib (ldiskfs) with connectx-5 cards, and I
have a maintenance window coming up where I have the opportunity to
upgrade it.

Which is likely to cause less breakage:
* stick with 2.10.8 on server and the annoyances with multi-rail /
discovery when talking to our new system
* upgrade to 2.12.9, sticking with the same OS major version
* upgrade to 2.15.1 including a jump to RHEL 8 / rocky 8 (depending on
licencing as we seem to have lost our HA add-on)

I can't upgrade the old 2.7.5 clients, as this system is already on
the decommissioning roadmap for next year

Many thanks

Andrew