It's been over a year since Western Digital unveiled its 5 TB and 6 TB variants of the Red NAS-oriented and Green Eco-oriented hard drives. After the long wait, the company is finally making the 5 TB and 6 TB Red Pro and Black drives available.

WD's new lineup has lots of different versions, and each one has a very clear use case and purpose. For example, the WD Red drives are meant to be used in small-scale NAS applications with up to eight drives. The Red Pro drives are meant to be used in NAS applications that require even higher reliability and are meant for NAS systems with up to 16 bays. The Western Digital Black series is aimed at single-drive desktop use, and represents the company's performance-oriented hard drives.

The new 5 TB and 6 TB WD Red Pro drives feature everything that the lower-capacity parts do. They are optimized to operate perfectly in high-vibration environments and come with built-in shock protection. The shock protection is particularly interesting as it enables the drive to adjust the fly height of the actuator, choosing to keep it further from the platter to protect the data, or closer for higher read and write performance. Additionally, the drives come with the NASware 3.0 firmware, just like its older brothers.

One of the more compelling reasons to buy a Red Pro drive may be the warranty. While the Red drives for smaller-scale applications come with a three-year warranty, the Red Pro drives will be replaced free of charge in case of defect over a five-year period. Of course, they cost a couple pennies more, but for the convenience that may just be worth it, even if you aren't running a huge NAS with 16 drives.

The new WD Black drives come with a couple new updates, the most notable of which is the increased cache size (upping it to 128 MB) and the dual-core processor. It runs at 7200 RPM and WD says that all the improvements make it up to 29 percent faster than the 4 TB variant that was introduced previously. The StableTrack technology that the older WD Black drives (2 TB and above) featured is still present.

Despite the WD Black drives operating at higher speeds, and therefore higher temperatures, WD is still confident enough to pair them with a five-year warranty.

Note that the many different lineups exist because of differences in the drives. Manufacturers know, for example, that NAS users like to place their drives in RAID arrays, and therefore adjust the firmware accordingly. While you can place desktop-class drives, such as a WD Green, Blue or Black in a RAID array, it is highly advised not to do so in order to protect your data. A RAID enabled drive will spend less time attempting to read bad data using a feature called TLER (Time-Limited Error Recovery). A RAID controller typically considers a drive "broken" if it doesn't respond within seven seconds, while a desktop-class drive can keep on attempting to read a data block for up to 20 seconds, leading to RAID controllers dropping drives out of the arrays while they aren't actually defective.

Pricing for the 5 TB and 6 TB Red Pro drives sits at $269 and $299, respectively, with the 5 TB and 6 TB Black drives selling for $5 less each at $264 and $294. All drives are available immediately.

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