TITLE: FDISK and Cluster Sizes DOCUMENT ID: TID21696 DOCUMENT REVISION: 1 DATE: 03AUG94 ALERT STATUS: Yellow README FOR: NA NOVELL PRODUCT and VERSION: Novell DOS 7 ABSTRACT: NA --------------------------------------------------------------------- DISCLAIMER: THE ORIGIN OF THIS INFORMATION MAY BE INTERNAL OR EXTERNAL TO NOVELL. NOVELL MAKES EVERY EFFORT WITHIN ITS MEANS TO VERIFY THIS INFORMATION. HOWEVER, THE INFORMATION PROVIDED IN THIS DOCUMENT IS FOR YOUR INFORMATION ONLY. NOVELL MAKES NO EXPLICIT OR IMPLIED CLAIMS TO THE VALIDITY OF THIS INFORMATION. --------------------------------------------------------------------- ISSUE: The cluster (or file allocation unit) is the smallest amount of disk space DOS can assign to a file. Partial clusters cannot be given to a file, nor can two different files occupy space within the same cluster. As a result, there will always be some degree of unusable space on a disk. Statistically, the average file will "waste" about half of a cluster. Therefore, a large number of small files will waste much more space than a small number of large files. It is desirable to have very small clusters, in order to minimize the wasted space. You can control cluster size by strategically choosing the size of your partitions or logical drives (from this point, this document will use the term "partition" to refer to both partitions and logical drives). Partitions and are created and deleted with the utility FDISK.COM. Note that the process of deleting a partition will destroy all information contained within. The following table shows the cluster sizes that correspond to various partition sizes. PARTITION SIZE FAT SIZE SECTORS/CLUSTER CLUSTER SIZE -------------- -------- --------------- ------------ up to 15.9Mb 12 bit 8 4K 16 - 127.9Mb 16 bit 4 2K 128 - 255.9Mb 16 bit 8 4K 256 - 511.9Mb 16 bit 16 8K 512 - 1023.9Mb 16 bit 32 16K 1024Mb - 2Gb 16 bit 64 32K It is theoretically possible for FAT size and cluster size to vary from this table. For example, it is possible for a partition up to 8Mb in size to have 12 bit FAT and 2K clusters, which would give more efficient usage of space. However, Novell DOS 7, DR DOS 6.0, and MS DOS 6.x all use the implementation listed in this table. Some DOS versions earlier than 4.x may vary from this table. Also, it is possible that some 3rd party partitioning utilities may not follow this implementation. If you are not sure what utility was used to create your DOS partitions, you may wish to check your actually cluster size by using Novell DOS 7 CHKDSK.EXE, which will list the number of "bytes in allocation unit". You can also use 3rd party utilities such as Norton's SYSINFO.EXE. --------------------------------------------------------------------- Any trademarks referenced in this document are the property of their respective owners. Consult your product manuals for complete trademark information. ---------------------------------------------------------------------