netapp flash cache
Does it cache writes now? I just tried poking around for some docs but didn't find an immediate answer. Last I read/heard(4-5 years ago) their flash cache was for reads only(for the org I am in where we have roughly 90% writes, caching reads in flash doesn't excite me).
3PAR(I am a customer) does flash caching as well, but their architecture too limits the flash cache to reads(unless things have changed recently). EMCs flash cache could/can do both reads and writes, never used it so don't know how well it works, sounded good though.
I think removal of SCSI overhead from a typical enterprise array will probably not have a noticeable impact on overall performance(as in reduction in enough cpu cycles to do other things, of course in the 3PAR world those operations are performed on ASICs).
But if/when NVMe gets to the same price (maybe +/- 10% even) as typical SCSI/SAS, then there will be little reason not to do it just because ..well because why not. I think while the overhead of SCSI does introduce latency, I also expect it to be more robust. In talking with one NVMe startup CEO and his team about a year ago I was kind of scared the levels that you need to go to in order to get high performance (direct memory access etc), just seems..very fragile.