The 3-2-1 rule can aid in the backup process. It states that there should be at least 3 copies of the data, stored on 2 different types of storage media, and one copy should be kept off-site, in a remote location (this can include )
Whenever your workload can be mainly processed within your RAM, even a slow HD pool is nearly as fast as an ultimate Optane pool.
In my tests I used a pool from 4 x HGST HE8 disks with a combined raw sequential read/write performance of more than 1000 MB/s. As long as you can process your workload mainly from RAM, it is tremendously fast. The huge fallback when using sync-write can be nearly eliminated by a fast Optane Slog like the 900P. Such a combination can be nearly as fast as a pure SSD pool at a fraction of the cost with higher capacity. Even an SMB filer with a secure write behaviour (sync-write=always) is now possible as a 4 x HGST HE8 pool
(Raid-0) and an Optane 900P Slog offered around 500-700 MB/s (needed for 10G networks) on OmniOS. Solaris
with native ZFS was even faster.