Document 1208
FDISK CLUSTER SIZE

Description:

The cluster size that FDISK will select depends on the size of
the partition being created. The cluster size for a particular
partition size is shown in the following table:

Partition Size    Bytes/Sector    Sectors/Cluster   Cluster Size

0 - 127.9MB          512                   4             2K

128 - 255.9MB        512                   8             4K

256 - 511.9MB        512                  16             8K

512MB - 2GB          512                  32             16K

The cluster size is adjusted for different partitions because of
the use of a 16 bit File Allocation Table (FAT). DR/PC/MS DOS
use a 16 bit FAT and can therefore keep track of 65,536
clusters. If each of these clusters is 2k, 2k x 65,536 is about
127.9MB. If a larger partition is desired, the cluster size has
to be increased since the number of clusters is limited. Thus
the cluster size goes to 4k. 4k x 65,536 is about 255.9MB. At
that point, the cluster size has to be adjusted again.

If a third party utility is used to create a partition using
different cluster sizes, the bytes per sector setting must be a
power of 2 (..,64,128,256,512,1024,..).

The above information is based upon using the FDISk utility
included in the February Business Update of DR DOS 5 or in
releases manufactured after that time. This includes DR DOS 6
and DR MULTI-USER DOS.

The following is for releases of DR DOS prior to 2/1/91

 Partition Size   Bytes/Sector    Sectors/Cluster   Cluster Size

  0 - 63.9MB          512                4               2K

  64 - 127.9MB        512                8               4K

  128 - 512MB         512                16              8K