3 TB from Seagate with the Barracuda XT
 

This drive has the SATA interface with average reads of 129.7 MB/s and writes of 127.7 MB/s in HD Tune Pro, for access times of 11ms. For comparison, a 7200.12 with 500 GB platters manages 103.9 MB/s reads, so the gain is 25% and would seem to indicate that the drive has 4 x 750 GB platters.

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