Mac OS X,  Mac OS X Server

Mac OS X Server: Group Quota's

Group Quotas enable limitation of how much data a given group can write to a volume.  The .quota.group file at the root of a given volume can be used to control quota settings. 

Note: the .quota.group file is hidden (as can be seen from the leading . in the filename.

The edquota command can be used to enable Group Quotas on a per-volume basis.  In this regard it is important to remember that an AFP mount is considered a volume to the client systems.  Each different AFP Share Point is a separate volume to the client system.