After you have decided on the function of your machine, you need to consider carefully the sizes of the partitions you're going to create. If you are not careful, the partitions will be too small to store your information and may cause the computer to freeze when a partition runs out
of available space and is unable to accommodate new data. Try to estimate future usage as best you can. It is very difficult and very dangerous to try to resize live partitions. Be careful not to undersize your partitions.
Following are some general partition size ranges for a typical system:
Partition size depends on usage. The /var directory normally contains log, temporary, and lock files.
Partition size depends on usage. If the machine is used for user accounts, enough space needs to be allocated to hold the users' files.
2-3 times the RAM installed in the machine
The ranges cited above are for small desktop to large server installations, and are not set in stone. In planning and sizing partitions, you have to take into account what you will be doing with the system.
For example, on a system that just serves news or is a database server, it might be fine to have a relatively small root partition, which would contain any home directories, and a large /var partition. A separate /tmp partition is usually not a bad idea under any circumstance.
The following MouseOver illustrates typical partition sizes matched to machine function.