Our previous system of managing disk space involved no quotas. If a user on a particular partition wrote lots of files, deliberately or not, which filled the filesystem, no one else on the filesystem could write or edit files until some free space was created. When a filesystem neared full, staff would move some users to filesystems with more free space. To lessen impact of some groups on the rest of the community, these groups were isolated to their own "private" partitions. But in any case, the excessive usage of a single user could inconvenience all others sharing the same partition.
With quotas, we can remove the impact on other users. Each user is given a soft and a hard quota. The soft quota can be temporarily exceeded by the user for up to a week, during which time the user will be reminded he is over quota. The hard quota can never be exceeded, protecting other users on the same filesystem. If the user fails to get under soft quota during the week, he will be prevented from writing to the partition (create new files or modify existing ones) until he is back under quota. The buffer for faculty members between soft and hard quotas (the amount which they can temporarily exceed their quota) is typically 250MB.