If you’re looking for a two-drive NAS, it’s likely that you’re considering it because you want the fault tolerance that RAID 1 offers. Otherwise, you could buy a single-drive NAS with more usable storage capacity for significantly less of an investment. The Pro Duo does offer a turnkey solution for those who don’t want to purchase and install their own drives into a competing BYOD NAS enclosure.
However, you do pay a price when choosing the LinkStation Pro Duo—both in features and in performance. The performance ranks at the bottom of our two-drive charts and near the bottom of Buffalo’s own products. While you might not save any money with a BYOD solution, you can typically pick up significant performance improvements and a richer feature set. Many comparably-priced BYOD products include "business features" that the Pro Duo has, like Active Directory support, and "consumer" features that the Pro Duo lacks, such as media servers and built-in download clients.
I also felt that the RAID recovery process was sub-par. There are two reasons to have fault tolerance in a storage system: to ensure that no data is lost and ensure access to data. On the first account, the Pro Duo did, in fact, ensure that no data was lost when we failed the drive. Although our method of "failing" the drive while in operation may have caused some problems, drives tend to fail when they are in use, not turned off.
But on the second account, the Pro Duo failed the test. The device should have continued operating in a degraded mode until we could have replaced the drive. We were surprised with the Pro Duo shut down, and even more surprised when it wouldn't reboot with the single drive of the RAID pair. This seems to be a design shortcoming.
There are several ways that manufacturers can choose to rebuild a failed RAID array. Some manufacturers such as LaCie and QNAP, automatically detect a new replacement drive and automatically start a rebuild. Buffalo, on the other hand, chooses to involve the user, which we first discovered when we reviewed the TeraStation Pro II.
Unfortunately, there is no guidance in the user manual on what to do if a drive fails and how to rebuild the array. In fact, the only mention of RAID setup in the manual is on page 24. There is just a screen shot of the Disk Management Raid screen with the instructions: "Configure your RAID settings here". Since devices that support various levels of RAID are more complicated than single drive units, manufacturers should include additional information about how to set them up, as well as how to recover in the event of hardware failure.
Buffalo continues to differentiate its LinkStation product line by splitting them into a consumer line (Live and EZ) and a business line (Pro and Pro Duo). With the exception of the EZ, all of the LinkStations use the same processor, so it seems like the differentiation is more based on marketing than technology. So w hy not include the richest possible set of features in a single product line? Manufacturers like Synology and QNAP have done that, and are gaining traction in the US market.