Mailinglist Archive: opensuse (880 mails)

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Re: [opensuse] Slow file copying on openSUSE 12.3
  • From: "Carlos E. R." <robin.listas@xxxxxxxxxxxxxx>
  • Date: Fri, 16 Aug 2013 00:46:32 +0200 (CEST)
  • Message-id: <alpine.LNX.2.00.1308160013040.5725@Telcontar.valinor>
Hash: SHA1

On Thursday, 2013-08-15 at 17:40 -0400, Greg Freemyer wrote:
On Thu, Aug 15, 2013 at 1:45 PM, Carlos E. R. <> wrote:

1 MB per track? Then a 1 TB disk would have a million tracks? Surely a track
is bigger.

Yes and no. If a 1 TB drive has 4 heads, then it 250,000 cylinders.
But a cylinder would have 4 tracks, so yes it is 1 million tracks
total, but only 250,000 per platter surface.

I'll let you do the math, but this is how I do it:

A 7200 RPM disk does 120 revolutions per second.

At its fastest speed it is reading (or writing) data continuously, so
that is 120 tracks per second continuous at its fastest

Not possible. Moving the head from one track to the next takes some time It moves an stimate (it is an analogic voice coil), then reads track metadata to learn where it is, and if it is not where it should, it moves again.

Acording to the datasheet of the Seagate Barracuda 7200.12 (because I have it at hand) the track to track time is 1 mS (average time is 8.5 mS). 1 mS seek time, plus 8.3 mS read time per track (1 revolution), that is 9.3 mS per track. That is 107 tracks per second maximum :-)

However, the same datasheet says:

Track density: 236 ktracks/in avg

If the platter has 2" and something usefull surface radius, thats about .5·10⁶ tracks per platter side, which is even more than the number you said, so you are about right and I wasn't.

But it surprises me the high number of tracks and the low linear density (1 meg per track?), or I'm looking at it wrong.

I have two other figures:

Recording density: 1413 kbits/in max
Areal density: 329 Gbits/in2 avg

At a 2" radius, that's 6,28· of circunference, so that's 8,8781×10⁶kbits, or about 1,109 MB

So you are right :-)

- -- Cheers,
Carlos E. R.
(from 12.3 x86_64 "Dartmouth" at Telcontar)
Version: GnuPG v2.0.19 (GNU/Linux)

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