Whenever a user performs a write, the number of written bytes counts toward that user's quota. What causes the write doesn't matter; the effect is the same. Most of the time, using applications to create or modify files causes writes, but system tasks can also affect the quota. For example, pasting a file from a remote computer adds to the user's quota the number of bytes copied. Copying a file from one folder to another on the same volume adds bytes (in effect, the file's bytes double for the user's total), but moving a file doesn't add bytes. Deleting a file doesn't remove the bytes from the disk quota until the user empties the Recycle Bin. And it's important to notify your users that file compression doesn't count*the real size of the compressed file is counted against a user's disk quota. Because the disk-quota system tracks usernames, if a user takes ownership of another user's file, the file's bytes are added to the acquiring user's quota total.

Installing software adds bytes and frequently causes users to exceed their quotas. If you configure disk quotas to deny write privileges when users reach their quota, software installation might become complicated. For that reason, always install software in one of the following ways:

  • Log on to the computer as Administrator (disk quotas don't apply to the Administrator account).
  • Create a user that's a member of the Administrators group for the purpose of installing software. For that user, specify an extremely large quota or disable quotas.

Unfortunately, you can't configure on a user-by-user basis the option to deny write privileges when the quota is reached; this setting is global for the volume. You can only disable quotas or change the number of bytes for individual users.