Single-instance storage is a system's ability to keep one copy of content that multiple users or computers share. It is a means to eliminate data duplication and to increase efficiency. SIS is frequently implemented in file systems, e-mail server software, data backup and other storage-related solutions. In the case of an e-mail server, single-instance storage would mean that a single copy of a message is held within its database whilst individual mailboxes access the content through a reference pointer. However there is a common misconception that the primary benefit of single instance storage in mail server solutions is a reduction in disk space requirements...