[svlug] 2 part Linux question

Jeffrey Siegal jbs at quiotix.com
Thu Jul 10 11:42:42 PDT 2003

Donald K. Wilson wrote:
> I did this recently and cut the time from about an hour and thirty
> minutes to just under twenty minutes for an 8 GB disk by using a
> block size that equals the cylinder size. I don't remember the
> calculation - it was last week, after all - but I think you multiply
> the size of the sector (usually 512 bytes) by the sectors per
> track and multiply by the number of heads. dd allows you to
> multiply on the command line using 'x'.

The reported "cylinder size" on all modern hard drives is a fiction; the 
number of bytes per cylinder varies with more on the outside and less on 
the inside.

You got the benefit you did by using a large block size.

I'd also make sure the drive has DMA enabled (hdparm -d1), assuming the 
drive and motherboard support this properly (almost all do).

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