Hard Drive data rates
John Wendel
john.wendel at metnet.navy.mil
Fri Sep 28 19:07:11 UTC 2007
Lamar Owen wrote:
> On Friday 28 September 2007, Karl Larsen wrote:
>> I was lead to mis-understand the data rate of my new SATA hard
>> drive. It indicated that the data rate was 3 GB/sec. But some checking
>> with Google said the Hard Drive makers are very free with their units.
>> To be specific a SATA drive is 3000 MegaBits/second. This boils down to
>> about 375 MB.
>
> Due to the 8B/10B coding used in SATA, you can divide the bitrate by ten and
> not eight to get the byterate. Thus, 3Gb/s is 300MB/s at the wire. The
> semi-standard way of differentiating between bits per second and bytes per
> second in specs is to use a lower-case b for bits, and an upper-case B for
> bytes, but unfortunately not everyone follows that.
Your talking about the wire speed. The REAL speed is determined by the
disk drive. You're lucky to get 75MB/s with a desktop drive.
Regards,
John
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