LaCie is prepping dual drive RAIDed storage box delivering up to 275MB/sec across its USB 3.0 link. The product is the 2Big USB 3.0, with two hard drives, a maximum capacity of 4TB - ergo 2 X 2TB 3.5-inch hard SATA drives - and either RAID 0 or RAID 1 configurations. It uses a dual USB 3.0 SATA and RAID bridge controller from …
not really 4TB is it?
More like 3.72TB before filesystem overhead.
USB 3.0 is not the bottleneck.
I should make it clear. USB 3.0 is not a bottleneck here; it's the speed at which the drives can pump data into the USB 3.0 pipe, which is why multi-drive USB external storage arrays are a good thing in terms of bumping up deliverable I/O speed through the wire.
There is no file system overhead.
There is no significant capacity lost due to overhead.
They are using different units of measurement.
Hard drive manufacturers consider a TB to be one trillion bytes.
Most operating systems report a TB to be 1024^4 bytes.
Its like the rope manufacturers are selling rope by the foot. But you are measuring it in meters, dividing it by 3 and wondering where the missing rope went.