/var use is (like all good things unix-ish) arbitrary but, apart from logs which often do grow to considerable size, is also the default location for 'in use' files like databases. For example,, both postgres and mysql will default to /var as the home for their potentially sizable database file. Rule of thumb? Declare /var to be LARGE in size. Most ofthe server crashes I have to deal with arise from exhaustion of the /var file system.

Cheers