Regarding the loud drives, I did switch my user directory back to the iMac's internal 1TB drive. I hear the same amount of read/write activity but it is so much quieter than the Thunderbay. I cannot emphasize enough just how loud the seek and write noise is with this enclosure and the four 4TB HGST NAS drives. It really does not seem to be head parking.
I might try adding the RAID to the privacy area in Spotlight but that defeats a lot of the purpose of even using the RAID for a user directory.
Seriously considering surrounding the shelf the enclosure sits on under desk with 2" acoustic egg crate foam to silence it/deaden some of the noise.
Wondering if worth the effort. Even though the RAID is benchmarking at 5x faster than the internal HDD, I'm not sure I'm seeing that in real world use. I still have Yosemite and applications on a 128gb SSD attached via Thunderbolt.
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You may want to just send it back and get different drives. My Seagate 5TB disks x8 (yes, 8) in RAID 5 are astonishingly quiet (picture included). You can barely hear them, and I sit right by them in my movie room. The only sound I hear it the sound of them being "on," which is 100% background noise, and never any whirry/grindy nonsense. And I'm VERY sensitive to these things.
That kind of stuff will drive you mad otherwise, potentially, so path of least resistance might be more ideal for you.
Also, RAID 5 is really, REALLY poor for small random read/random write, so I'd recommend not using it for a user directory anyway. I'm not even kidding when I tell you you can get benchmark results in the 5-10MB/s range of read and write when it comes to lots and lots of small files. Just try copying a large folder of tiny files off your RAID 5 to an external/internal SSD. You'll see how miserably slow it will be. RAID 5 comes into its own with larger files where read/write speeds are excellent.
Yes, I know I need to dust my shelves better. I am man. It's just my nature to be half-arsed about cleaning.