faster than flash
only because they have GOBS of memory I am sure. I had a VAR come to me a few years ago (after EMC dropped some cupcakes on our CIO). Said they could sell me an array with a TERABYTE of cache (at this point for some reason they shifted from selling EMC to selling HDS). I sort of laughed, I said yeah I know you can, but we can't afford it so why bring it up.
Looks like their high end box has up to 4.5TB of memory and up to 36TB of flash cache (not sure if that is a read or read/write cache)
For HP 3PAR (what I know best of course) their high end system has up to 3.5TB of memory and up to 48TB of flash cache(read cache on that system). "Only" six nines of availability there (though they also commit to 6 nines on any 4-controller 3PAR system).
I do realize the extra 9 is not a trivial amount of extra availability. Not sure what level of availability HP may commit to if you throw in peer persistence between two arrays(automatic/transparent failover without any external boxes or complexity).