The QNAP TS-239 Pro has basic NAS features that allow you to use the device as an FTP server, a DNLA media server, an iTunes server, a print server--that supports up to three printers--and so on. Each feature worked as intended, with a simple and straightforward setup.
The QNAP TS-239 Pro impressed us with advanced features like Download Station, Surveillance Station, built-in iSCSI target service (which is usually only available in enterprise NAS servers), AES 256-bit volume-based encryption and dual-Ethernet. We didn't try out the iSCSI target service, but the rest worked well and as intended. The dual-Ethernet, unfortunately doesn't make the NAS' throughput any faster (it's only for fail-safe and load-balancing), but is nonetheless a plus.
As a network storage device, the NAS' primary feature is to provide storage space for the network, and this is where the TS-239 Pro excels. The NAS supports SMB protocol, which means it can be easily accessed on a local network just as you would access another Windows computer. The NAS also supports Macs. Any Mac OS X computer in the network will find the TS-239 Pro automatically and will add it to the storage device list in the Finder. Unfortunately, the TS-239 doesn't support Time Machine (a backup function available in OS X 10.5 or later).
We tested the QNAP TS 239 Pro in both RAID 0 and RAID 1 configurations and it excelled in both, especially the read test.
In RAID 1, the configuration that offers high data security at the expense of storage amount and performance, the QNAP TS-239 Pro scored 176.6Mbps in writing and 292.4Mbps in reading. This is much higher than the 120.1Mpbs and 206Mbps of the My Book World Edition. Nonetheless, they were both bested by those of the Synology DS209+, which got 240Mbps and 322Mbps for the write and read tests, respectively.
In RAID 0, the speed-optimized configuration, the QNAP TS-239 Pro improved over its RAID 1 performance with 223.9Mbps for writing and 373.9 for reading. These numbers were very close to those of the top dual-bay NAS performer, the Synolgoy DS209+, which had a RAID 0 read of 256.3Mbps and a write test of 375Mbps.
All in all, the QNAP TS-239 Pro is one of the top-three performers among all NAS servers we've reviewed; however, we found that the gap between its write speed and read speed was larger than what other NAS servers experienced.
(Longer bars indicate better performance)
Overall, the QNAP TS-239 Pro also worked smoothly in our testing process and stayed very cool, even during the heavy loads. However, we found it a bit noisy, enough to be a bother if you use it in a quiet environment.
Service and support
QNAP backs the TS-239 Pro with a one-year warranty; this is short for a storage device. Technical phone support is available from 8 a.m. to 5 p.m. PT, Monday through Friday. On the QNAP Web site, you'll find applications and firmware downloads, as well as a forum where you can find help from other users or search for existing solutions.