@HoneyBadger, This is Linus Tech Tips, you expected better?
From the distant past;
I get that the odds of failure were pretty low, especially with the spare in there (which is 27 drives, based on the calculators) but if you add three more, you could run 3x 10-drive Z2, get roughly the same space (84.6TB vs 85.6TB) and tolerate two drives per vdev failing. You're definitely in a nice secure space there, as well as having three vdevs to drive performance up even more.
(Obviously the answer for MAXIMUM PERFORMANCE is "mirrors" but then you're talking about needing 48 drives for the same usable space, taking into account spares.)
Also, at around the 18:00 minute mark Linus/Patrick talk about the SLOG options that the competitor offers, as well as Patrick advising against an Optane "write cache" because of the better ability of SSDs to tolerate random write workloads but honestly, odds are very good there were zero sync writes on this array anyways because it was set up for access from Windows servers, likely as SMB - so no syncs there unless forced by the client software. (And again, odds on that approach zero.)
If there were sync writes though (NFS clients, or forced via
sync=always
) A fast Optane device (or maybe one of those fancy expensive NVRAM cards we love over in the SLOG benchmark thread) could help save write amplification on the SSDs, although it might require adjustment of
zil_slog_bulk
if you're using 1M records.