There are several things to consider when you're comparing hard drives for your NAS. First, pricing is exceptionally important due to the magnified expense of buying more than one drive for each system. Reliability, and its close cousin, reputation, are a close second. Performance is often an afterthought for home users, but it plays a larger role if you are running applications either on or through the NAS.
Price is a big part of the equation because mass storage is expensive. It doesn't matter if you pay for an eight-bay NAS with small drives or buy a smaller NAS with larger drives. You pay somewhere. The first step in building a NAS is the extensive research and planning involved if you go the DIY route. You can always go the more expensive but easier route and buy Western Digital's complete systems that come loaded and configured from the factory.
We often see a price drop on the existing models when new products come to market with a new capacity tier. That works out in our favor. The new 10TB Red 10TB currently sells for $380, which comes to $1,520 for a four-drive array. Dropping a capacity tier, the 8TB Red drives sell for $247 each, so a five-drive array costs just $1,235. Provided your NAS supports five drives, it would be better and cheaper to use five 8TB Red drives instead of four 10TB drives. You will gain more usable storage capacity and even gain a slight performance advantage in most cases.
Western Digital's reputation for reliability is also important. A recurring case study from cloud provider Backblaze has moved this from simple word-of-mouth to quantifiable reliability statistics. The reports are far from ideal, but they are the best we have. HDD vendors have historically hidden this type of data from the public eye but Backblaze has ignored the potential fallout and given us an extensive look behind the curtain. Western Digital and HGST products perform very well in the reports I've read over the last few years.
The new Helium-filled Red series appears to be tuned to favor high sequential performance more than random workloads. The Reds are a great fit if you're looking for a drive to handle core NAS features and very little application work. If you plan to use heavy virtualization or use the NAS for applications, it would be better to look at Red Pro or true enterprise models like the new Gold series. With that said, the Red family has progressed to a point where the performance is more than most of us can use. Just as NAS systems have overachieved through increased processor performance and features, the Red product line has done the same. The new Helium-filled 10TB and 8TB Reds are often faster than the Red Pro 6TB that WD released just a few years ago.
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