In October, WD introduced a new My Cloud external storage device with revamped software geared toward mobile devices. The single-drive machine offers up to 4TB of capacity, but as we noted in our initial coverage, it lacks internal redundancy. Fortunately, there's a new My Cloud device that addresses that shortcoming. The My Cloud EX4 has the same software as its single-drive sibling, but it packs four hot-swap drive bays configured by default in a parity-protected RAID 5 array.
The EX4 is a handsome-looking box NAS box. It's relatively compact, at 8.2" x 8.7" x 6.3", and the bulk of the enclosure is made of metal rather than plastic. WD is particularly proud of the all-metal bays, which supposedly allow drives to be swapped in just a few seconds.
As one might expect, the EX4 is available with WD's NAS-specific Red drives pre-installed. There's also a barebones version that allows users to add their own storage. WD's compatbility list includes drives from its own Blue, Green, and Black families. The EX4 has also been validated for use with several models from Seagate, HGST, and Toshiba. Drives that don't appear on the compatibility list should work, as well, but WD says official compatbility testing has been limited to top-selling products.
The drives are managed by a Linux-based operating system running off embedded flash memory. Other internal hardware includes a 2GHz ARM-based processor and 512MB of RAM. On the outside, the My Cloud EX4 sports dual USB 3.0 ports, Gigabit Ethernet jacks, and power connectors. The dual power connectors might seem a little odd, especially since the EX4 ships with only one power brick. However, WD says the power adapter is one of the biggest points of failure for NAS devices. Supporting a secondary power source makes sense for a device focused on redundancy.
The EX4 isn't cheap: the barebones version is priced at $380, and you can expect to pay $800 for the 8TB version, $950 for the 12TB model, and $1150 for the 16TB variant. But there's a lot of built-in functionality, including DLNA support, an FTP downloader, and a BitTorrent app. WD has made an SDK available to developers, too, and third-party apps are already available from Wordpress, phBB, Joomla, and others. With devices like this on the market, I have to wonder how many enthusiasts are still building their own home file servers.