So besides the obvious btrfs answer, what about ceph as clustered storage with very fast connectivity?

There is also BeeGFS, I haven't used it but /r/datahoarders sometimes touts it.

Not for linux but I have been keeping an eye on M Dillons DragonFly BSD where he has been working on HAMMER2, which is very interesting.

I don't know much but bcachefs has been making more waves lately also.

I think the bottom line is that people need to have good backup in place regardless.