> -----Original Message-----
> From: PCBUILD - Personal Computer Hardware discussion List
> [mailto:[log in to unmask]]On Behalf Of Don Cooley
>
>
> Patrick
>
> The figures below are interesting.  If you have a 7GB hard drive
> you can use
> 4K clusters.  If you use a 7GB up you can use 8K cluster.  Now when you
> figure it out you will find that a 8GB drive with 8K clusters
> only gives you
> someplace in the vicinity of 7GB of useable space.   May be
> better to use a
> 7GB drive or to format a 8GB drive to use 7 GB and make use of the 4K
> clusters.  The larger the cluster size the more he waste space.


The size of the cluster has nothing to do with the total amount of
wasted space.  It is actually the total number of files stored (and
the size of them) that will affect how much space is wasted.

First of all, think of a cluster as a storage box.  When we speak of
8K or 16K or 4K clusters, we are talking about how large the storage
box is.  In other words, how many bytes of data can be stored in the
cluster.

The next thing to understand is that when ANY file is written to
a disk, the entire cluster (or clusters) is(are) reserved for that
file only -- no other data can be written into that cluster,
no matter how much space is left unused.  (THIS is where the wasted
space comes from)

Now that the stage is set....

If I have a 15K file (doesn't matter what KIND of file) and I store it
on a disk using 4K clusters, the file will use one complete cluster for
the first 4K of data, a second complete cluster for the next 4K of
data, a third cluster for the next 4K and a fourth cluster for the
remaining 3K of data.  The fourth cluster (as well as the first three)
is now reserved for that file only.  So I have wasted one kilobyte
of storage space in that last cluster. (4K total minus 3K used)

If I store the same file on a disk with 8K clusters, then it will
need two clusters to store the file and will have 1K of unused space
in the second cluster.  So again, I have the same amount of wasted space.

If I store the file on a disk with 16K clusters, then it will only
need one cluster which will also have 1K of unused space.

Naturally a different file size will have a different outcome, but one
of the interesting side points is that (in my example) the FAT for the
16K disk will need to keep track of the location of only one cluster for
the file.  But the FAT of the 4K disk would need to keep track of 4
clusters -- thereby using up four times as much of the FAT storage area
to keep track of that one file.  So the 4K disk __could__ end up
being less efficient than the 16K disk.

PS:  When you format an 8Gig drive, you will get 8Gigs of storage
space regardless of whether it has 8K, 16K, or 32K clusters.