Using the four standard drive bays, one can now have 16TB of internal storage! This can be arranged in many different ways: one 16TB volume, 4 X 4TB volumes, 2 X 8TB volumes, etc.
The MPG Pro Workstation is typically configured with one 2-drive stripe for the Master volume (for performance), and one 2-drive mirror for Time Machine volume (for fault tolerance), based on the assumption that 4TB of capacity is plenty to cover the most recent work— full external backups should always be made in addition.
Capacity and performance
With the 7K4000 having a 4TB capacity, I expect that average speed across the first 3 TB will be notably higher than the 3TB Hitachi 7K3000, because larger hard drives are faster (on average). In short, if you need only 3TB of capacity, getting the 4TB capacity and simply ignoring the last 1TB is likely to net you real benefits.
I started by making a 4-way RAID-0 stripe using SoftRAID 4.
My DiskTester fill-volume test takes a long time to run (fills the entire volume), so my report will be 24-48 hours off. Get DiskTester as part of diglloydTools. I always use the command line (Terminal) version, but a simple GUI is also included.
My initial testing shows outstanding speed similar to the Hitachi 3TB 7K3000. Which is plenty, because with a 5-way stripe, that Mac Pro internal bus becomes the bottleneck.
disktester run-sequential --test-size 32G ht4 Allocating maximum size contiguous file on "ht4" (14.6TB)... 14.5TB (99.9% of volume size) TEMP FILE: /Volumes/ht4/disktester-test/DiskTester-Temporary-Test-File Using test size of 32GB, 4MB at a time at start (0%), within a 14.5TB test file. Iteration 1: writing...589MB/sec, reading...564MB/sec Iteration 2: writing...579MB/sec, reading...572MB/sec Iteration 3: writing...592MB/sec, reading...571MB/sec Iteration 4: writing...586MB/sec, reading...571MB/sec Iteration 5: writing...590MB/sec, reading...572MB/sec Wednesday, April 4, 2012 4:18:32 PM Pacific Daylight Time, volume "ht4" (14.6TB) ------------- Averages for "ht4" (32GB/4MB, 5 iterations) ------------ Iteration Write MB/sec Read MB/sec 1 589 564 2 579 572 3 592 571 4 586 571 5 590 572 Slowest 579 564 Fastest 592 572 Average 587 570 Median 589 571 Range 13.0 8.13 Command "run-sequential" executed in 572.69 seconds on Wednesday, April 4, 2012 4:28:05 PM Pacific Daylight Time