Thanks for the replies, Richard.

Can SSTATE_DIR be shared across build hosts with different OS's  (Ubuntu 18.04, ubuntu 20.04, etc, RHEL)?

Our build hosts are somewhat ephemeral.  Occasionally we need to swap out a build host for another one. So to bring on a new fresh build host and have it cooperate correctly with the other build hosts and the PR server, what does it need?  I understand having the NFS mounted SSTATE_DIR, and using the PRSERV_HOST variable set correctly. But what else?  Does the new build host need access to a shared PERSISTENT_DIR or a shared BUILDHISTORY_DIR?

What happens if the shared SSTATE cache get corrupted and has to be deleted?   Won't that cause all the PR server values to reset?  We just want to make sure we know how to recover from a situation like that.
Thanks a bunch.
Rusty