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Disk Preparation
Disk Clusters
An article from when disks were growing and FAT/32 was king..
Disk Preparation


With the phenomenal increase in hard disk sizes in recent times, the old problem of cluster sizes and disk wastage is beginning to rear its ugly head again.

This was originally an issue with 2GB hard disks using FAT16, but virtually disappeared when FAT32 and ~10Gb hard drives were king. Now in early 2002 we are seeing average hard disk sizes of 40GB or more and once again, the importance of setting several smaller partitions for usability and space saving has become important.

As can be seen below, various file systems have varying cluster size limitations. So what? Well it is possible to save a great deal of space by choosing the right file system. Disk space is wasted by lots of smaller files, which actually take up more space than their actual file size: each file on your hard drive uses fixed size blocks of disk space called clusters.

For example, if a file is 33KB in size and the drive's cluster size is 32KB, then 31KB will be wasted, because the file will use the next 32k cluster to store its remaining 1KB

FAT/FAT16 (DOS/Windows 95/Windows NT)

Partition Size Cluster Size
0 - 127MB 2K
128 - 255MB 4K
256 - 511MB 8K
512 - 1023MB 16K
1024 - 2047MB 32K

Note: FAT16 is limited to 2.1GB per partition.

FAT32 (Windows 95B/C and Windows 98/SE):

Partition Size Cluster Size
512MB or less 4K
8GB - 16GBB 8K
16GB - 32GB 16K
32GB or more 32K

Note: A partition formatted as FAT32 can only been seen in Windows 95 version 950B/950C or Windows 98/SE. Earlier versions of Windows [95a upgrade], DOS 6.22, and Windows NT 4.0 cannot natively recognize FAT32 partitions.

NTFS (Windows NT):

Partition Size Sectors / Cluster Cluster Size
512MB or less 1 512bytes
513MB - 1024MB 2 1K
1025MB - 2048MB 4 2K
2049MB - 4096MB 8 4K
4097MB - 8192MB 16 8K
8193MB - 16,384MB 32 16K
16,385MB - 32,768MB 64 32K
32GB or more 128 64K

Note: You cannot use NTFS file compression if your cluster size is larger than 4K.
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