For me:
Areca 1880ix-12 - $650
Sans Digital 8-bay box - $399
(miniSAS cables included)
$1050 driveless
8x WD RE-4 2TB HDDs @ $200 ea. - $1600
The drives cost is higher than the storage sub-system hardware. Even 6 of those drives would be more; $1,200 ( 6* $200 ). If more to SSDs either capacity is going to drop dramatically or the cost will skyrocket much higher.
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Mind you, the Pegasus R6 won't do anywhere near 800+MB/sec in RAID 6.
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That is drive and RAID controller dependent. 6 SSDs and might (if not throttled by the controller's parity engine. )
Their HDDs are 150MB/sec each, while mine are only rated at 138MB/sec each... which I know is about right, since I got 1101MB/sec in a RAID 0... divided by 8 = 137.625 each.
Even more evidence that really talking about differences in RAID controller performance than anything to do with the enclosure-to-system interconnect speeds.
and go much faster than anything the Pegasus can ever hope for over Thunderbolt.
The general 'claim' is that Thunderbolt is the root cause issue. There is gating issue with the Pegasus before the data ever hits the Thunderbolt network. That is what I'm pointing out.
No, but I linked to a benchmark using my exact card and SSDs, which IS a benchmark, is it not? The answer is yes, it is.
Yes you can push more data through a x8 link than a x4 link. That pragmatic issue is how much is that going to cost you. Real projects have multiple constraint dimensions to them. Budget, capacity , and bandwidth. More than a few of these extreme benchmarks are drag racing events. Most businesses aren't run leveraging Top Fuel drag racing cars.
Apple's hyperbole "Thunderbolt is the fastest, most versatile I/O technology there is. " is bogus. It isn't the fastest possible alternative. The pragmatic question though is it fast enough for most people. For 900+ MB/s folks, yes it is.
And in that very benchmark, you can see 3000MB/sec flowing free and sustained. You won't see that on Thunderbolt without some serious effort and expense far beyond what a single PCIe RAID card can do in a single slot.
It takes extra effort and expense because Thunderbolt never was targeted for that kind of work. For "capacity is secondary to bandwidth" issues the MP 2013 has at least one PCI-e SSD in a single slot.
For a SAN header node 3000MB/s probably has far more wide spread market traction than for a single user workstation. The new Mac Pro is not a good match to be a SAN header node. It is far more aimed at being a client to a node with that kind of throughput so that 3-4 folks can concurrently get 1000MB/s like throughput to the machines on their desks.