COW and volume management?

> it is a write-anywhere-*ish* (but not really)

ish? Fully I believe. The only exception to write anywhere I am aware of is the uberblock. IIRC you basically have two logs, one for the uberblock only and one for everything else.

I believe NetApp does the same thing, the root inode, just like ZFS's uberblock, is constrained to a few known locations to avoid having to read every byte on every disk on a cold start.

> (but not really) kind of filesystem with a log (journal) hanging off its side for performance.

No, both metadata and data are always written to a new location when updated. There is no update in place neither in ZFS nor in NetApp WAFL.