Of course your disk head will not move randomly. If you have swap space in the middle of a disk between a constantly busy home partition and an almost unused archive partition, you would be better of if your swap were in the middle of the home partition for even shorter head movements. You would be even better off, if you had your swap on another otherwise unused disk, though. 3.4 Some facts about file systems and fragmentation Disk space is administered by the operating system in units of blocks and fragments of blocks. In ext2, fragments and blocks have to be of the same size, so we can limit our discussion to blocks.
Files come in any size.
They don't end on block boundaries. So with every file a part of the last block of every file is wasted. Assuming that file sizes are random, there is approximately a half block of waste for each file on your disk. You can guess the number of files on your disk by the number of allocated inodes on a disk. Had I chosen a block size of 4 KB, I had lost 4 times this space.