Given that replay times are primarily single core CPU bound, I'm interested in whether the much higher single core performance of HEDT CPUs with only 64Gb or 128Gb RAM combined with Optane and/or NVMe can't provide a much faster replay times for a much lower price for both witness and full RPC nodes.

If Optane can act as extra RAM (via cache) then the RAM limitations of 64Gb (for LGA 1151 motherboards) & 128Gb (for LGA 2066 motherboards) are overcome and the dramatically faster single core performance will dominate.

@bobinson did a replay in little over 5 hours on a Xeon Gold 6142 with "block_log, block_log.index and shared_memory.bin all on Optane". This CPU is clocked at 2.6 Ghz base / 3.7 Ghz boost with a single core PassMark of only 1909 (based on similar Xeon Gold 6126). This is faster than @anyx's Xeon Gold 6130 (at 1636) but much slower than HEDT CPUs.

By comparison the i9-9900K does a PassMark of 2909 single core and the i7-7740X does 2622 single core. Even the lowly i5-8400 does 2335.

With the same all on Optane setup these HEDT CPUs with much faster single core performance can bring replay times under 3 hours.

@themarkymark & @anyx: If replay times are less than 3 hours then multiple cheap HEDT machines (even without ECC) will provide much greater overall uptime & performance than a single Xeon Gold for both witness & full RPC nodes.