This is from the high density VRD here: http://www.arubanetworks.com/wp-content/uploads/DG_HighDensity_VRD.pdf
"VLAN Pooling
Use VLAN pools in the virtual AP profile for large networks that require more than one subnet for HD WLAN clients within a specific floor or building. Doing so restricts the size of the broadcast domain, thereby limiting unnecessary traffic.
Keep each VLAN subnet within a VLAN pool to a 24-bit subnet mask. Do not have more than 10 VLANs within a pool so that broadcast or multicast traffic does not
consume too much air time access."
Amigopd and ArubaOS integration VRD here: http://www.arubanetworks.com/wp-content/uploads/Amigopod-AOS-Integration-AppNote.pdf