🚀 go-pugleaf

jim@jfitz.demon.co.uk (Jim Fitzpatrick) said:

>A friend of mine has just had his faulty hard drive changed under
>warranty. The original was 850Mb and contained 600Mb of data, which he
>backed-up onto tape. The new one is 1Gb. 

>With the 600Mb of data restored, the 1Gb disk reports 150Mb free -
>i.e. apparently 850 Mb used by only 600Mb of data. The only difference
>between the setups is that his 850Mb disk had Win3.11 installed,
>whereas during the upheaval he took the opportunity to change to Win95
>with the 1Gb disk.

>Any idea what may be going on here? He's checked for temporary files,
>swapfile size...i.e. all of the obvious things. I don't know the size
>of his clusters (oo-err! fnarr, fnarr!) but you'd need a hell of a lot
>of small files to spirit 250Mb away like that. Win95 will be taking up
>more room than Win3.11, and of course 1Gb is the unformatted capacity,
>but both of these things together should account for a few tens of
>megabytes, not hundreds.

Jim,

You hinted at the most likely cause, reluctant though you are to believe it.
If the 1GB drive is configured with a single partition, then the size of his
clusters (aka ALUs or Allocation Units) are 16K (16,284 bytes).

The only method I know to minimize this "slack space" wastage is to
partition the hard drive into smaller logical drives.  (This may not be all
that inconvenient for your friend, as it sounds as though he has a fairly
adequate tape backup unit).

I *do* know another way, but that involves moving to an entirely different
File System (i.e. another OS).

Here's the low-down on what your clusters will be for ranges of
partition-size:

	Partition size		ALU size in bytes

	64MB-128MB		2,048
	128MB-256MB		4,096
	256MB-512MB		8,192
	512MB-1GB		16,384
	1GB-2GB			32,768

... and so forth -- get the pattern?

This is a feature of the FAT file system.  Personally, I stick to partitions
of 254MB, just to be on the safe side.

And BTW, if you need to convince yourself that I'm not lying, try the
following (assuming no disk compression is in operation):

At the DOS prompt:

o  "cd" to an empty-ish directory (c:\temp would be a good one).
o  type "dir" and note the number of bytes free.
o  type "echo x>fred" (to create a piffling file).
o  type "dir" and note the number of bytes free.
o  subtract original bytes free from new bytes-free to see how many bytes
your piffling file *really* takes.

Also, you could take the total number of files on the disc (likely to be
around 16,000 for 600MB "real" content), and multiply that number by half
the known ALU size to give you an approximate indication of slack space.

I can't resist, I'll do it now based on this estimate ...

ALU-size is (suspected to be) 16K, so half that is 8K.  Multiply that by
16,000 and you get 131,072,000 (if I pressed the right buttons).

Well, there's some food for thought, anyway.

Good luck & best wishes

Neil
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Neil Trotter, Holmfirth, UK
Telephone:  +44 (0) 1484 534420          e-mail:  neil@nook.demon.co.uk
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