There are a surprising amount of users in the market for high performance RAID-capable drives at a friendly price point. Their search commonly ends with NAS drives. The NAS HDD segment is actually a newer classification that provides a great value segment for DAS usage.
While the WD Reds are marketed specifically for DAS arrays from one to five drives (along with their more typical NAS usage), the Seagate HDDs are only directly marketed for NAS usage. The only other options from Seagate for small-scale DAS usage are the Terascale and Enterprise Capacity (ES.3) HDDs, which are considerably more expensive. This leaves the Seagate NAS HDD as the go-to value offering for DAS usage from Seagate.
Most NAS units, especially in the one to five bay category, are constrained to the speed limit of a single gigabit Ethernet port. A single gigabit Ethernet port is limited to an effective speed of 120-125 MB/s, and this leads many prosumers to utilize the faster speeds of DAS RAID arrays. Both drives are resilient to heavy workloads, and provide plenty of endurance for typical prosumers with small-array DAS usage. The drives also feature various spin-down states, and communicate directly with RAID code to repair any data loss.
The Seagate NAS HDD draws less power than the Red, and is great for arrays that will spend a lot of time in various spin-down states. The Seagate NAS HDD also excels at sequential read performance, largely due to its adaptive algorithms that detect sustained sequential read and write activity. The Seagate NAS HDD will fare well with large file access models, such as audio and video streaming and editing.
Most SMB and SOHO users will not be utilizing a RAID 0 in their DAS, unless they dealing with replicated data protected by strong backup schemes. However, in the prosumer space there will be a stronger chance of utilizing RAID 0 arrays as fast scratch disks for content creation and modification.
In this usage model, the WD Red wins at all random workloads by a convincing margin. In RAID 0, the WD Reds also put forth a commanding lead in sequential write performance; leaving lower power consumption and faster sequential read speeds as the only advantages for the Seagate NAS HDD.
In RAID 5 usage, the most common type of DAS array, the WD Red leads with random workloads, but the margins are not as large as with RAID 0 usage. In parity environments, the WD Red still wins overall, making it the best choice for the majority of DAS workloads. Users searching for sequential strength in parity environments will fare well with the Seagate NAS HDD.
Consumers will always look for the best value, and there is no denying the obvious price advantages of using a NAS HDD in RAID. The emergence of NAS HDDs provide resiliency in RAID environments, and good-enough warranty periods for consumer DAS applications. We expect to continue to see this trend expand as NAS HDDs mature.