maybe i misspoke - at one point there was battery backed DDR ram they used in PCIe, but by the time i came around they were using Fusion IO PCIe devices, which i guess were NAND flash, not DDR. or, alternatively, that is how it was explained during onboarding - "it's like DDR on a PCIe card, so the iops are 1000x that of SAS 10k drives"

unless you're talking about our experiment of tmpfs - then yeah, the use case was "genewitch heard bill gates say 640k should be enough for anyone; here's a super beefy machine to test that theory; theory tested." We didn't run the site live on that machine for more than 10 minutes or so, we switched it back to the fusion-io backed server immediately. It was a proof of concept about one of the things we could do with these new servers - read replicas with the DB in tmpfs for extreme speed and no IO blocking.