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Re: [OM] Western Digital My Passport Essential USB 2.0-Powered External

Subject: Re: [OM] Western Digital My Passport Essential USB 2.0-Powered External Drives
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Mon, 02 Feb 2009 20:51:53 -0500
AS I said the other day, disks spend a lot of time just trying to get to 
were they're going and, once they get there, waiting on the correct data 
to rotate around to where the head is.  They all seek to where they're 
going at very similar rates and, assuming the same RPM on the platters, 
they all wait at the same speed.  Actual data throughput gets dragged 
down by all the mechanical delays.

But do be aware of what you're comparing.  If you are simply reading 
from the USB drive into memory but reading and writing between the two 
SATA drives then the write operation has the SATA drives at a big 
disadvantage.  Writing takes longer than reading and the reading from 
drive 1 can't go any faster then the writing to drive 2 once the cache 
is full.

Chuck Norcutt


C.H.Ling wrote:
> 5x! Did you ever made a real comparison? I got 22MB per second for USB and I 
> can't get over 30MB with SATA to SATA (two hard disks inside the same PC). I 
> believe the HD sustain rate and other overheads in the computer limited the 
> data rate a lot.
> 
> C.H.Ling
> 
> ----- Original Message ----- 
> From: "Moose"
>> I'm simply not buying any external HD which is USB 2.0 only. eSATA is
>> WAY faster, 5x the speed, and only a very few $ more, if that. Maybe it
>> shouldn't make a difference for a drive planned for backup use only, but
>> it does for me. I simply find it easier when the process goes faster.
>>
> 
-- 
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