Re: XP Partition size
From: Alex Nichol (alexn.mvpdts_at_ntlworld.delete.com)
Date: 09/11/04
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Date: Sat, 11 Sep 2004 11:05:53 +0100
Steve N. wrote:
>
>Number of cylinders
>Number of blocks per cylinder
>Number of sectors per block
Blocks per cylinder is not a basic. A multi-platter hard disk has
Cylinders, defined by position of heads radially; 'Heads' or tracks,
(one on each platter) and sectors (512 bytes each, along the track).
On a modern HD the number of sectors per track varies according to
length of track - increasing by zones as you go out from the middle.
This CHS direct description puts very awkward limits on things. As
defined you cannot have more than 1024 heads, but can have 64 tracks -
implying 32 dual sided platters, which you never meet in a PC drive. So
for practical purposes addressing is now done in sector number from the
start. But there is still seen to be a logical head and sector number
around when you are partitioning and the partitioning software makes
partitions aligned on these logical cylinder boundaries; every 8MB.
This is sorted out to an actual cylinder, track and sector by the
drive's own electronics
This being called Logical Block addressing (LBA) *may* be what you are
thinking of, but it is *not* a division used in the underlying hardware:
certainly not in the sense of being some multiple of sector. Or
Someone may be using 'block' where everyone else still uses 'track' .
Or you *may* be using 'blocks' where anyone else uses 'clusters' -
the 'allocation units' of typically 8 sectors (4K bytes) for allocating
space to files in a file system - this is *not* related to partitioning
at all. .
-- Alex Nichol MS MVP (Windows Technologies) Bournemouth, U.K. Alexn@mvps.D8E8L.org (remove the D8 bit)
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