The MCS-7855I-1.5-ECS2 is specifically targeted at unified messaging deployments, with less required disk drive capacity because messages are stored on a separate server. The MCS-7855I-1.5-ECS2 is a MCS 7855I-1500 targeted at Unity deployments supporting unified messaging. A single MCS-7855I-1.5-ECS2 can support up to 7500 unified messaging subscribers or voice messaging subscriber if the messages are stored on a separate server.Media Convergence Server 7855I-1500 is used with Cisco Unity for unified messaging deployments.