Oye... Not this againnnnnnnn
"NetApp's controller-located FlashCache, and caching both reads and writes unlike the NetApp technology which is a read cache only."
From: http://blogs.netapp.com/efficiency/2011/02/flash-cache-doesnt-cache-writes-why.html
NetApp’s Data ONTAP does something uniquely different from the majority of other storage vendors’ products; it’s optimized for writes. Indeed, write optimization was one of the original design criteria for Data ONTAP back in 1992. Dave Hitz himself explained this many years ago in TR-3001 (since updated). In brief, Data ONTAP eliminates the “Disk Parity Bottleneck” through its use of WAFL to coalesce a group of temporally located write IOs; pre-emptively “defrag” if you will this group of I/Os based upon the best possible allocation unit or “tetris” available; calculate parity for the entire lot while in memory, and stripe the lot of them across all available drives during the next write event (aka consistency point, CP).
"Data ONTAP eliminates the “Disk Parity Bottleneck” through its use of WAFL to coalesce a group of temporally located write IOs" -- That part is done via a write cache battery-backed DIMM(s)...