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From: philip@pescadero.Stanford.EDU (Philip Machanick)
Newsgroups: comp.sys.mac.misc,comp.sys.mac.hardware
Subject: Re: VANISHED!  12 Mb on a 80 Mb Hard Disk
Keywords: hard disk space missing
Message-ID: <1990Jul25.174247.8259@Neon.Stanford.EDU>
Date: 25 Jul 90 17:42:47 GMT
References: <1990Jul24.202754.13288@usenet.ins.cwru.edu>
Sender: news@Neon.Stanford.EDU (USENET News System)
Reply-To: philip@pescadero.stanford.edu
Organization: Computer Science Department, Stanford University
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In article <1990Jul24.202754.13288@usenet.ins.cwru.edu>,
bhatlas@pyrite.SOM.CWRU.Edu (Sunil Bhatla) writes:
> 
> The last thing I need is a shrinking hard disk...
> 
> My 80 Mb internal hard drive (on a Mac IIx)  shows:
> 
>  "66,137K in disk  12,600K free"
> 
> But when I catalog all the files (including the desktop)
> I can only account for 56 Mb.  I tried Redux and a couple of
> disk cataloguing programs, and they all tell me the same thing.
> 
> Someone suggested I zap the PRAM, but that didn't help.
> 
> Where is the additional 12 Mb?   HELP!! [You mean 10 Mb?]
> 
One thing you could try is Get Info on some of your files. You will
observe that the actual space a file takes up is rounded up to the
nearest multiple of 1024K. Losing bits of space in this way is called
internal fragmentation. If I recall rightly, disks up to 32M allocate in
chunks of 512K, and the unit size goes up with each multiple of 32M.
This is one good reason to partition a large disk. If each partition is
smaller than 32M, you presumably get files allocated in smaller chunks.
(Someone correct me if I'm wrong - I haven't looked at this stuff in detail.)

This can be important if you have lots of small files, since the average
lost will be about half the chunk size per file.

Philip Machanick
philip@pescadero.stanford.edu