Cache on system with 64 GiB non ECC

[SmallBarky]

I’ll just point you to the ZFS Primer and to read the documents for the version of TrueNAS you are running, hardware section on memory sizing.

ZFS Primer

Also take a look at this recent post in another thread

Optane SSD size for SLOG / L2ARC

General answers SLOG Rule 0: You probably do not need a SLOG. Rule 1: A SLOG should have PLP, high endurance and low write latency. Rule 2: Size should hold two transaction groups, so 2*5 s by default. (Larger does not hurt, save for the wallet.) 16 GB M10 Optane fall somewhat short on endurance and throughput for SLOG; however they make nice boot devices. Although the size of a M10 would be sufficient, the real entry point for an Optane SLOG is a 100 GB DC P4800X. L2ARC Rule 0: You probabl…