From: aland@chaos.cs.brandeis.edu (Alan D.)
Subject: Re: "Get Info" reports different size when file is moved [FAQ?]
Reply-To: aland@cs.brandeis.edu
Organization: As little as possible
Distribution: usa
Date: Thu, 30 Jul 1992 15:14:09 GMT

milbouma@esvax.dnet.dupont.com writes:

>This subject has come up before, I think, but I need a refresher, prompted by a
>question from a curious fellow Mac support person.

Is this in the FAQ list?  Rusty? *grin*

>How does the Finder and Get Info calculate/report the amount of disk used by a
>document?

The Finder and Get Info are correct...  The file is 2048 bytes long.
(because a Word file has some overhead to it, beyond the actual text
contents).

>Mac with system 7 is used to create an MS-Word file (with one word in it).
>Get Info reports file is:		3K (2048 bytes used)

This hard drive has either a 1.5 or a 3K block size (minimum amount of
disk space a file can take up).

>Document is transferred to floppy.
>Get Info reports this copy is:	2K (2048 bytes used)

A floppy has either .5K or 1K blocks; I think .5 but I'm not positive;
therefore this is correct (eg. not wasteful).

>Floppy put into system 6 Mac, Get Info shows same as previous (2K)

None of this is system-dependent...

>Document copied to system 6 Mac's hard drive (a large drive ~1.2GB)

>Get Info reports this copy is:	17K (2048 bytes used)

The block size on the 1.2GB drive must therefore be 17K.

>Why would 17K of disk space be needed to store a 2K document.  I know there is
>some overhead with format info, directory info and pointers, but
>a 17:2 ratio?  Would sectors on a large capacity drive be much larger (some
>minimum greater than 2K)?  Or does it relate to a difference in the way system
>6 and system 7 handle these things?

There are, in the current (September) issue of MacUser magazine, a few
"common threads" in the text.  One is this name that keeps popping up,
'Adam Engst'.  In the letters, "Shareware Top Hits" article, etc...
The other is that you should partition large hard drives ('large'
being greater than 31.5 Meg) in order to efficiently allocate space.
At least, for drives on which you expect to store small documents.

Basically, there are a limited number of blocks which can be allocated
on a volume (I believe there are 32768 +/- 2), and if you have more
than that number of blocks, the formatter increases the block size so
you don't exceed that number.  Therefore, if you have a need for
storing many small files (around 1-2K), you should (ideally) make it a
30 meg partition (which gets you a block size of 1K).

For larger files, you can have a larger partition, since the
approximate percentage of wasted space is that much smaller...  If
this makes any sense.

So, you should partition your 1.2 gigabyte drive into multiple volumes
(using LaCie's SilverLining, FWB's Hard Drive Toolkit, or Drive7 (the
company which makes this one escapes me...)).  These are the most
'common' and fully-featured disk formatting/partitioning programs.

One thing you should be aware of (and avoid) is that you want to
partition the drive using "hard partitions" (true SCSI partitions)
rather than "soft partitions" (large files which the Mac OS is fooled
into thinking are hard partitions).  Hard partitioning allows you to
mount the volumes when you boot w/out extensions & if you move the
hard drive to another Mac; they can be used as boot drives; if one
crashes, the others will usually be fine.  With soft partitioning, if
the "real" SCSI partition fails, all your soft partitions are goners
as well.

Well, there's my treatise on 'mass media block sizes' and
partitioning...  I hope you enjoyed it.  Inaccuracies, etc. should be
sent to me, so I can correct my mistakes...

	-=Alan
Newsgroups: comp.sys.mac.system