Re:In-memory vs. disk-based DB: Why do you need a larger tha...
by zamadatix on Saturday September 02, 2023 @05:35PM
(#37365729)
FWIW I think you have the aggregation backwards, dual socket Genoa would have 24 channels of DRAM but sacrifice some of the PCIe lanes for the interconnect.
Re:In-memory vs. disk-based DB: Why do you need a larger tha...
by wtallis on Saturday September 02, 2023 @05:52PM
(#37365843)
Dual-socket Genoa would be 24 channels at DDR5-4800 (38.4 GB/s) for a total of ~921.6 GB/s. Typical PCIe configurations are 64 or 80 lanes per socket for dual-socket, so 128 or 160 lanes total, at PCIe 5.0 speed that's ~504 GB/s for 128 lanes total or ~630 GB/s for 160 lane configurations.
Single-socket Genoa would be 12 channels of DRAM (~460.8 GB/s) and 128 lanes of PCIe 5.0 (~504 GB/s), but none of the previous comments were specifically about single-socket Genoa and I wasn't going to silently switch from considering dual-socket in one sentence to single-socket in the next sentence.
Do you mean a RAID0 of just two or four NVMe SSDs? It's absolutely ridiculous to count aggregate DRAM bandwidth across two CPU sockets and not do the same for PCIe lanes. A fair comparison is that Genoa has about twice the DRAM bandwidth as it has PCIe bandwidth, though in a fully-loaded database server some portion of the PCIe bandwidth will be used for networking rather than storage.