Data de-duplication technology fundamentally changes the role of disk in backup. It gives users a cost effective way to retain their backup data on disk for weeks or months, making their file restores fast and easy and increasing the number of available recovery points. Disk-based backup appliances that utilize data de-duplication technology can offer an IT professional a combination of advantages - including ease of use, extended retention, fast restores and cost savings. They can also make replication of backup data over WANs a practical tool for providing offsite protection for backup data.