At 12:56 PM -0400 8/17/2010, iJohn wrote:
On Mon, Aug 16, 2010 at 1:45 PM, onelucent <oneluc...@mac.com> wrote:
These are compact, come in much larger sizes than the early days
and can be purchased with 7200 rpm mechanisms.
FWIW, using a 7200 RPM drive as a USB 2.0 or even FW 400 attached
external drive doesn't really buy you anything extra.
Unless you use eSATA, USB 3.0, or FW 800 the throughput of the drive
is going to be limited by the bus used to connect the external drive.
It's sort of like buying a performance car that you know you'll only
drive around town and never take over 45 MPH.
Ok. You are correct, to a point.
The raw media transfer rate of a 5400 rpm disk *is* faster than USB 2
or FW400 can throw data. Typical is 800 to 1200 Mbps (depending on
various factors - number of heads/platters, cache size, etc). By
comparison, an inexpensive 7200 rpm drive can usually throw at 1200
to 2000 Mbps.
The problem is access time, aka seek+latency - the time it takes for
the heads to reach a track, then the delay until the required sectors
spin around to reach the head. Quite often I've found that 7200 rpm
drives will outperform slower drives simply because of the much lower
access time, plus the fact that they usually have larger buffers, so
you can read or write a whole track at once.
YMMV.
- Dan.
--
- Psychoceramic Emeritus; South Jersey, USA, Earth.
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