Waste not, want not
by Alan Zisman
(c) 1997. First
published in Computer Player, July 1997
So you got a new computer or added a new hard drive on
your old one.
2 gigabytes. 2 billion bytes. Sounds like lots of space. But add a few
games, an office suite, some other applications, and suddenly, you're
about out of room. Add up everything you've installed, and you'll find
four or five hundred megs of free space has gone missing.
You've run into the problem known as cluster slack.
This problem is a result of history-most of us are
still using file
systems designed in the early 1980s. The people who designed the DOS
Allocation Tables (FAT) to keep track of files, put an upper limit on
number of possible addresses that could be assigned to a disk. Since
3.31 (1987), there's been a fixed number of addresses, but as
get larger, cluster sizes grow at the same rate. This enables DOS (and
related operating systems) to use drive partitions as large as 2 gigs.
Here's the down side.
Files get stored in a series of these clusters... and
two files can't
share a single cluster. So if a file fills up, say, five clusters plus
1 byte, all but 1 byte of that sixth cluster is wasted. On average,
file wastes one-half a cluster. With relatively small drive partitions,
that's not too bad. For example, my 240 meg D: drive, uses 4 kb
and has 1,623 files... wasting a mere 3 megs of space.
But I also have a 840 meg C: drive, requiring 16 kb
clusters with 8,408
files... that's about 135 megs wasted. And if I'd set up my system as a
single 1080 meg (1 gig) drive, I'd need to use 32 kb clusters, so the
or so files would waste about 320 megs-over 30% of my drive space! Even
with drives getting ever cheaper, I don't want to be paying for that
space that I can't use.
To check this on your own computer, PC users can run
the old DOS standby,
CHKDSK at a DOS prompt... it will report, among other things, the
of files, and the allocation unit (or cluster) size. Multiply the two
and cut the answer in half for an estimate of cluster waste. And by the
way, Mac owners can't gloat-they have exactly the same problem.
You can minimize the waste, however.
* Create multiple partitions. As we've seen, there is
much less waste
with smaller partitions. Unfortunately, the DOS partitioning tool,
destroys your data if you make any changes to your partitions. Instead,
check out Partition Magic, from Power Quest, a non-destructive
* If you've got the Windows 95 Plus Pack, you've got DriveSpace 3 (DS
3). While designed as a disk compressor, it can be used to virtually
cluster slack... set it to a paradoxical 0% compression, and you'll get
rid of waste space, as all your files are combined into a single, large
file that pretends to be a hard drive. Sounds weird, but it works...
with virtually no performance loss, since you're not actually
and expanding your data. (But DS 3 needs a 104 kb driver when you boot
to DOS-a major problem running older DOS games).
* Upgrade to a more advanced operating system. OS/2 has an optional
HPFS file system, while NT sports an optional NTFS system. Both use a
way of keeping track of files, resulting in the equivalent of 512 byte
clusters, and virtually no waste. But changing operating systems is a
drastic solution... and if you boot to DOS, you won't be able to read
HPFS or NTFS partitions.
* If you bought a computer with Win 95 pre-installed since Fall 1996,
you probably have Win95B. (Check in Control Panel/System... if you have
Win95B it will say '4.00.950B'). That lets you use FAT32... a new and
version of FAT, with much smaller cluster sizes, and support for
larger than the DOS 2 gig limit. Even with Win95B, however, most
are continuing to use the older, wasteful FAT16 system.. You can change
a Win95B system to FAT32, using the DOS FDISK, but you'll destroy your
data and have to reinstall everything. Again, Partition Magic provides
a non-destructive alternative. Be careful not to use old disk utilities
with FAT32, and note that while you can boot to Win95B's DOS, you can't
boot to earlier DOS versions.
One way or another, you might as well get as much hard
disk as you've