SSDs will have higher latency than ram, and I seriously wonder if they actually can hit 7GB/sec, or only theoretical. Ram is faster, always, in latency and bandwidth.
> I've benchmarked some not-so-old servers (the entire box, not a VM!) as capable of only 35 GB/s streaming reads from main memory!
Then you have either a low-end server or something is very wrong (I think you benchmarked wrong, see below). You should be getting maybe 15 GB/sec per channel, so 4 channel = 60GB/sec, for a decent server you may well have 6 or 8 channels. (figures may be a bit off but 35 is puzzling me).
You may have measured on a single core, but each core has its own mem reading stuff so it should multiply up if your benchmark uses extra cores.
Anyway, I have to get back to work on my dual-core haswell. Good luck!
(Edit: 15 * 4 = 60, not 80, corrected)
So keep in mind that the SSD I'm referring to can read at 7 GB/s. Not seven gigabits... 7 gigabytes per second. I've benchmarked some not-so-old servers (the entire box, not a VM!) as capable of only 35 GB/s streaming reads from main memory! So these days "disk" is more like "5x slower memory". It used to be 100-1000x slower.
I told one customer to get a 16x PCIe gen 4 adapter card with 4 NVMe M.2 ports on it. This would -- in theory -- be able to pump out 28 GB/s of reads, equivalent to a 200 Gbps NIC. Total storage would be 32 TB with CoTS 8TB drives.
That's a mind-blowing amount of IO in a single box!
The hardware has the capability, it's the software and inability to utilise that is the bottleneck now..