Managing all the bytes on a disk has a lot of overhead. A most disks internally uses 512 byte "Sectors" to store data. So you can manage data by 512 byte blocks (ie the BlockSize is 512 bytes). Now, some FileSystem's manage data in "FileClusters?" which is some multiple of the BlockSize. For Ext2/Ext3 for instance, this is by default 4k1? (although this can be changed). Microsoft took this to all new hights by having huge block sizes, up to 64k in size.
1?: 8 disk blocks
5 pages link to DiskCluster:
