re: Gnat-Mac and Disk space

re: Gnat-Mac and Disk space

[David Emery]

In article <1996Apr19.112413.53772@nova.wright.edu>,
jmatthews@nova.wright.edu (John B. Matthews) wrote:

...
> MacTen (out of the box) + gnat for Mac (off the net) takes up
> 47,671,668 bytes for 2968 files. That's 51 MB in a 94 MB partition
> but about 120 MB in a 1 GB partition.
> 
> Hope this helps.
> 
> John
> ----------------------------------------------------------------
> Dr. John B. Matthews
> jmathews@nova.wright.edu; john_matthews@ccmail.dayton.saic.com
> "Whom the gods would destroy, they first invite to program in C"

It's a real quirk of the MacOS file system that the minimum amount
of disk space used by a small file is a function of the size of the
file system/partition.  Apparently MacOS divides the disk into 1/N 
parts, where N is CONSTANT.  Thus, a 1GB disk drive (single partition)
will use 4 times as much space for a 10-byte file as a 250mb file
partition.  

The solution to this is to use disk driver software that partitions
the drive.  I'm currently using 135mb partitions (with a "double partition"
for all my Mac applications) on a 1GB drive.  (I use Silverlining for
disk driver/partitioning, but most good disk driver packages for the
Mac support multiple partitions.)  (I selected 135mb as the size of
a EZ135 cartridge, should I ever buy one, I know that I can completely
backup/restore a file system (without fancy backup programs) to a single
removable disk.  

Not only will partitioning save you disk space (particularly for things
like GNAT, which uses lots of very small files), it also improves disk
performance, etc.  

And, last but not least, you can install various OS on different partitions.
I'm currently running MacOS 7.5.1 on one partition, and 7.5.3 on another.
When my copy of MachTen arrives (hopefully next week :-), I'll install it
on a separate partition.

            dave

Re: Gnat-Mac and Disk space

[Robert Dewar]

Dave Emery said

"It's a real quirk of the MacOS file system that the minimum amount
of disk space used by a small file is a function of the size of the
file system/partition.  Apparently MacOS divides the disk into 1/N
parts, where N is CONSTANT.  Thus, a 1GB disk drive (single partition)
will use 4 times as much space for a 10-byte file as a 250mb file
partition."

This is of course a quirk exactly shared by DOS and any other system
using the FAT formats of DOS.

Re: re: Gnat-Mac and Disk space

[Gary McKee]

In article <emery-1904962024330001@line149.nwm.mindlink.net>,
emery@grebyn.com (David Emery) wrote:

 > The solution to this is to use disk driver software that partitions
 > the drive.  I'm currently using 135mb partitions (with a "double
partition"
 > for all my Mac applications) on a 1GB drive.  (I use Silverlining for
 > disk driver/partitioning, but most good disk driver packages for the
 > Mac support multiple partitions.)  (I selected 135mb as the size of
 > a EZ135 cartridge, should I ever buy one, I know that I can completely
 > backup/restore a file system (without fancy backup programs) to a single
 > removable disk.  

--------------------------------------------------------
David, The Mac OS addressing scheme is sensitive to the ubiquituous "powers
of two" syndrome. 

Consequently, your minimum file size will drop significantly if you reduce
your partitions below the "magic" 128k barrier.

I ran partitions for awhile at 127kb and the files were smaller. I also
took about a 5% performance hit running partitions so I reformatted my hard
drives and traded disk space for increased performance (albeit, only a
small improvement).

Your mileage may vary (YMMV).


--------------------------------------------------------------------
Gary McKee                           McKee Consulting
gmckee@cloudnine.com                 P. O. Box 3009
voice: (303) 795-7287                Littleton, CO 80161-3009
WWW home page =>                     <http://www.csn.net/~gmckee/>
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Re: Gnat-Mac and Disk space

[Arthur Evans Jr]

In article <AD9E60D296681D0F6@p2.denver2.dialup.csn.net>,
gmckee@cloudnine.com (Gary McKee) wrote:

> The Mac OS addressing scheme is sensitive to the ubiquituous "powers
> of two" syndrome. 
> 
> Consequently, your minimum file size will drop significantly if you reduce
> your partitions below the "magic" 128k barrier.

Close but not quite.  "Allocation block size grows by 0.5kb for every
32,767kb a partition is in size."  Thus a 127mb partition would have
block size of 2kb, and a 135mb partition would have a block size 2.5kb.
OTOH, if all you are concerned with is block size, you might as well go
up to the next multiple of 32kb.

The quote above is from the documentation that comes with FWB's Hard
Disk Toolkit software.  I'm suspicious of the number 32,767 -- I suspect
it ought to be 32,768.

Art Evans

Arthur Evans Jr, PhD        Phone: 412-963-0839
Ada Consulting              FAX:   412-963-0927
461 Fairview Road
Pittsburgh PA  15238-1933
evans@evans.pgh.pa.us