Question: I purchased a Baraccuda hard-drive (model ST3000DM001) that supports a maximum read transfer rate of 210 MB/s and SATA 1.5/3/6 Gb/s. My motherboard has a limited number of 6 Gb/s ports so I’d like to reserve them for when it’s really necessary.
When does a hard-drive benefit from a SATA 6 Gb/s port? Doesn’t it require a transfer speed of at least 375 MB/s to surpass the limit of SATA 3 Gb/s? Are there any other benefits of SATA 6 Gb/s vs 3 Gb/s ports?
Answer: A hard drive benefits from being connected to a 6Gbps SATA port when the drive is capable of sustained transfers faster than a 3Gbps SATA port support. ?
As you’ve surmised the ST3000DM001 drive can’t saturate a 3Gbps port based on its sustained read figure (210MB/sec => ~ 1.7Gbps) so any benefit you would get would be limited to burst transfers out of the cache — I would connect it to a 3Gbps port.
Spinning disk has a hard time getting up to 6Gbps speeds – In practice as of April 2012 only a few high-end 15K SAS drives can come close to 6Gbps performance (e.g. the IBM 44W2244 clocking in at 4.7Gbps), and the only drives that can saturate 6Gbps SAS or SATA connections are solid-state disks.