Work out group quota instantly with clear inputs, formula shown and shareable results.
Group quotas allocate shared capacity by project rather than by individual, which matches how research and engineering storage is actually consumed. Reserving a share for the largest project and dividing the remainder evenly is the usual starting point; XFS project quotas are generally preferred to group quotas because they follow directory trees rather than file ownership.
Group allocation
allocatable = size x (1 - reserve); largest group = allocatable x its share; each other group = remainder / (groups - 1)
Project quotas apply to a directory tree regardless of who owns the files, which is much closer to how teams think about storage and avoids problems when files are created by service accounts.
Usage is charged to the file's group ownership, so a setgid directory is essential to ensure files land against the intended project.