Why more partitions?

Most new computers are shipped with a large (20GB or greater) hard disk with only one partition. This causes three potential problems. First, it makes it hard to organise program and data, because you end up filling the C: drive with so many directories that finding anything becomes difficult. Wouldn’t it makes more sense to have a partition for programs, another for data and downloads, a third for games, and so on? Second, if you want to install an additional OS and want to use the file system native to that OS, you’ll have to back up your entire hard disk, delete the existing partition and create a new ones, then reformat and reinstall the operating system, programs, and data from scratch. In other words, not likely the third problem might come as a surprise. Large FAT partitions waste disk space. That may not be seem logical ----one big building with multiple rooms seems more efficient than several smaller buildings ----but it’s true. The problem stems from the fact that FAT file system was developed in the days when the floppy disks ruled and hard disk were small, and it was never meant to scale onto today’s multi-GB drives. It’s extremely inefficient at storing files.

 Why? To put it simply, FAT divides its partitions into grouping of sector called clusters. That’s fine, expect that FAT also limits the number of clusters in a given a partition to just over 65,000. As a result, as the size of the partition grows, so does the size of each cluster. For partition fewer than 128 MB, for example, each cluster will be 2k in size while a partition between 1GB-2GB has a relatively huge cluster size of 32k. And it’s not as if you have a choice; that 32k cluster size is the minimum for a 1GB partition, again because of the limited number of clusters the partition can have. FAT allocates disk space to files using whole clusters, even though very few files are precise multiple of the cluster size. The data occupying a file’s last cluster may fill the cluster completely or it may be as little as a single byte. With an even distribution of file sizes, the average wasted space per file will be half a cluster. On a 127MB drive with 2k clusters, your CONFIG.SYSfile, typically about 0.5k in size, wastes 1.5k. The small file on a 1.2GB drive with 32k clusters wastes 31.5k. On that same 1.2GB drive, a 100k file occupies just over three 32k clusters, with the majority of fourth cluster remaining empty.