Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
"Shailesh Humbad" <noreply@nowhere.com> wrote in message news:J2VRc.146310$fv.114963@fe2.columbus.rr.com...
> Bob Willard wrote:
> > Shailesh Humbad wrote:
> >
> >> With a RAID controller, one can stripe multiple hard drives for
> >> performance. How about an individual drive that has internally
> >> striped platters? It would have half the capacity, but (sometimes)
> >> twice the performance. Does it exist?
> >
> >
> > The IBIS drives of ~20 years ago used multiple R/W channels for
> > higher concurrent bandwidth, but that notion is not currently
> > cost-competitive: cheaper to add external RAID hardware (or even
> > software) to high-volume commodity HDs than to design HDs with
> > internal RAID and multiple R/W channels, since the low volume of
> > such RAIDed HDs would result in a very high price.
>
> Seems like if there are multiple platters in a hard drive, then there
> can be multiple, independent heads.
That is even possible with a single (but dual sided) platter.
There are several ways to multiply the transfer rate in a drive without
RAID.
1) Interlace a cylinder: block 0 on side A, block 1 on side B block 2
on side A, block 3 on side B, etc. etc, reading 2 blocks simultaniously.
Obviously only works on dual sided platters and the problem is that
the tracks have to be so perfectly aligned that the servo only needs
to track one of the tracks or that the sliders will need to have a piezo
positioning element incorporated so that they can track individually.
2) Have 2 or more head-elements side by side on a slider, reading
as many tracks in parallel by a single head: block 0 on track 0, block
1 on track 1, block 2 on track 0, block 3 on track 1, etc. etc, again
reading 2 blocks (or more) simultaniously. This can even be done on a
single sided platter. Again there is the problem of alignment as only
one track at a time can be followed by the servo system. The slider
however has to sit on a linear tracking arm to avoid skew problems.
Both reintroduce the servo tracking platter approach which was
abandoned for good reason in favor of the embedded servo approach.
> Now with peer-to-peer PCI Express, there would be plenty of
> bandwidth to support concurrent R/W.
What has that got to do with a single 'striped' drive.
> In addition, hardware RAID chips get cheaper every day.
What has that got to do with a single 'striped' drive.
>
> Even if the heads are not independent, there is lots of opportunity
> for performance benefit, especially if the drive knows enough to put
> contiguous blocks of data on parallel tracks.
What has that got to do with a single 'striped' drive.
> Of course, I'm assuming that on current drives, even though the heads
> are touching all the platters all the time,
I certainly hope not.
> only one head is actively reading from a track on a single platter at once.
> I don't know a lot about hard drives,
You don't say. But you do about RAID?
> so I leave it to the experts here to correct me.
>
> The reason I bring it up is that I would gladly take a 400GB drive
> down to 100GB, if I can get a 4x improvement in performance for
> sequential read/write. I only use 30-40GB of my drive now.
What has that got to do with a single striped drive?
Since when do you have to sacrifice capacity to gain performance?
Are you on drugs or something?
>
> You can might say to just use four 100GB drives, but then I need a
> bigger case, more power, and more cooling. My case is big enough to
> hold that many drives, but I think having so many drives is
> ostentatious, like a Lincoln Navigator. I'd rather have something
> small and fast, like a Porche.
>
> P.S. Most new types of computer hardware are expensive when they first
> come out. That's not to say that I know there is a market for such drives.
latter 0, 16:1, 32:2, and 48:3. Then any particular 
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