The 4-bay, hot-swappable TS-409 Pro Turbo NAS is designed for business users who require high performance, mass storage, and useful server features. Powered by 500 MHz CPU and 256MB DRII memory, the NAS supports a wide range of enterprise-grade server features, e.g. RAID 0/ 1/ 5/ 6/ 5+spare disk redundancy, Online RAID Capacity Expansion, Online RAID Level Migration, HDD S.M.A.R.T. and complete log system. According to Bjorn3d, "After more than a month of use extensively testing the TS-409 we were left very favorably impressed, especially with the seemingly endless array of features and available configurations.(The TS-409 Pro) offered good performance, data protection, and differentiated themselves from their competition."

The TS-409 Pro offers advanced RAID protection features which are rarely seen in other NASes of the same level. The unique Online RAID Capacity Expansion enables users to purchase the most cost-effective hard drives for initial server setup and upgrade to larger ones in the future. The Online RAID Level Migration allows users to start from one drive firstly and add more to upgrade the RAID level in the future with the data retained. As techPowerUp commented, "The added value comes from the extra disks and RAID levels supported. And when I say RAID I'm not talking about a simple onboard controller, the QNAP TS-409 Pro surprised me with RAID 6 (although slightly pointless with only 4 disks) and features like online expansion and migration. Such functionality is usually only found on advanced controllers you'd find in high end servers."

The TS-409 Pro supports multiple file sharing protocols for users to share files across Linux, UNIX, Mac, and Windows platforms. Abundant valuable server functions including File Server, FTP Server, Web Server and Printer Server, etc., are supported. Also, encrypted remote replication and backup to external devices are available to enhance data protection. Various data storage and management mechanisms, e.g. FTP server with SSL/TLS encrypted technology, SSH login, and web page SSL login are offered for secure data transfer and sharing. Moreover, the TS-409 Pro adopts silent fan and power-saving design which is excellent for long-term operation and deployment in small business environment without server room. The hot-swap design is supported for replacing failed hard drive of a RAID configuration without turning off the server to ensure non-stop services and minimize maintenance cost and effort. Besides, the HDD S.M.A.R.T. provides complete information of the hard drive status to prevent potential physical drive failure. The comprehensive log system summarizes the detail data access records and connection status to server administrator. All error and warning messages can also be sent via e-mail alerts for ease of maintenance.