How many music on hold servers are required in a trunk-only megacluster of Cisco Unified Communications Manager Session Management Edition?

When considering a megacluster deployment, the primary areas impacting capacity are as follows:
. The megacluster may contain a total of 21 servers consisting of 16 subscribers, 2 TFTP servers, 2 music on hold (MoH) servers (0 required), and 1 publisher
. Server type must be either Cisco MCS 7845-I3/H3 class or Cisco Unified Computing System (UCS) C-Series or B-Series using the 10K Open Virtualization Archive (OVA) template.
. Redundancy model must be 1:1.
Reference: http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/8_5_1/ccmfeat/fsgd-851-cm/fsmoh.html#wp1027431