Re: Harddisks: Seek, Read, Write, Read, Write, Slow ?
From: Folkert Rienstra (see_reply-to_at_myweb.nl)
Date: 07/15/04
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Date: Thu, 15 Jul 2004 17:27:25 +0200
Excuse if this appears twice.
I don't see *this one* in my "comp.sys.ibm.pc.hardware.storage" folder
although "Sent Items" says it was sent.
"Nathan McNulty" <525676@betaweb.com> wrote in message news:OauKdFeaEHA.1048@tk2msftngp13.phx.gbl
> Actually, what is happening is that the heads on the platter
> need to reconfigure themselves each time you read or write.
> It is a hardware limitation.
> By reading, the head can stay in the same location, but once it is told to
> write, the head has to position itself to change the magnetism of the
> sector of the platter it is on.
And that's why there is a write-to-read recovery (w-r) field in the make
up of every sector to allow the R/W channel to switch and the servo
to adjust the write-to-read element offset to center the write head.
http://www.hgst.com/hdd/ipl/oem/tech/noid.htm
> Then once you request to read again, the head has to move again.
That's actually automatic as the drive reads every servo field and
every sector to keep track of where it's at.
> It is the same as seek time
Nonsense.
> when you have two files on different partitions it is going to take
> longer to find those files than if they were right next to each other.
Nope. And read-ahead cache will have the contents anyway.
>
> Nathan McNulty
>
> kony wrote:
>
> > On Wed, 14 Jul 2004 17:53:52 +0200, "Skybuck Flying" <nospam@hotmail.com> wrote:
> >
> >
> > > Hi,
> > >
> > > Take these 3 concepts and then look at the implementation/performance:
[snip]
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