Mailinglist Archive: opensuse (880 mails)

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Re: [opensuse] Slow file copying on openSUSE 12.3
On Thu, Aug 15, 2013 at 1:45 PM, Carlos E. R.
<robin.listas@xxxxxxxxxxxxxx> wrote:


Fyi: per Linus, disk cache is internally organized in track size chunks. A
typical track can hold 1mb, so a 8mb cache on the drive controller can


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

A fast SATA drive transfers about 120 MB/second.

Thus 1 track = 1MB.

If the bottleneck is something other than how fast the media moves
underneath the disk head, then my analysis is wrong, but I really do
think that the limiting factor is how fast the drive is spinning.

Greg
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Greg Freemyer
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