Incorrect write speed displayed in Vista

[Jute]

I had to reinstall after a bios update and (it may have been the case before
but not that I remember) now my write speed is well under 1mb/sec, but it is
not that slow, I mean I can copy over 25 gig from one SATA drive to another
within about 20 mins or so. I remember seeing it at 14mb/sec which I though
was very slow, but now under 1mb/sec?!?!

It appears to clearly be an error with the aprox time given, but why now, it
seemed ok the other day. This is the case for both SATA and my WD external
hard drive, all of which have plenty of free space, just copying over my
pictures etc back to the main C drive.

Thanks.

 

[JW]

25 Gigabytes in 20 minutes is 200 Giga bits in 20 minutes which is 10
gigabits per minute which is 160 mb/sec according to my math.

 

[Jute]

Yes that's about right, not the displayed 500kb/sec or so, OK sometimes it
says 780kb/sec but can say as low as 18kb/sec.

 

[JW]

It is probably sampling individual reads so that if due to fragmentation it
had to do a seek before a read transfer could occur you would get a very low
rate indicated . It may do this so as to show the slowest overall time that
the transfer may take. I have noticed that transfers actually complete
before the progress bar gets to the end sometimes which is indicative of the
same symptom.