Hi, there’s a post-house I know who owns a Mac Pro 4.1, and an ATTO R380 Raid card for its Sonnet Fusion R800 Raid.
I didn’t upgrade to Mavericks and FCP 10.1 there because I read on ATTO website that latest drivers for R380 only supported Mountain Lion.
So you are on Mavericks ? Do you get a warning with ATTO notification tool on startup ?
Don’t know if your problems come from storage or anything else.
On this Mac Pro (2×2,66 GHz Quad-Core, 32Go Ram, ATI Radeon 5770, OSX 10.8.5, FCPX 10.0.9, Blackmagic Decklink HD Extreme 3D, “homemade” Fusion Drive), I’ve got good performances, but nothing astonishing.
A slight delay when pressing Play, some occasional beachballs or crashes, but I can work (feature-length documentaries).
Did you turn off App Nap for FCPX ? ( Get info on FCPX app, then check disable app nap )