We have covered plenty of NAS HDDs here at TweakTown, and the reason is simple: more and more users are purchasing NAS units every day. The expansion of NAS capabilities allows them to serve a much wider use-case than just a few years ago. In today's digital-content tsunami, many users are searching for the best solution to manage their vast trove of data, and NAS fits the bill nicely. There is nothing quite like centralized storage to ease the headache of managing data from the ever-expanding number of devices in the home.
Surprisingly, we receive many requests about which drives will work best in a Direct Attach Storage (DAS) usage model. NAS HDDs are also commonly used for value-oriented DAS usage models, in arrays from one to five drives. The primary focus has always been the use of NAS drives in NAS units, but in reality, they can serve a dual purpose. Pairing these small RAID arrays with the latest RAID controllers provides significant advantages over NAS deployment models. We have conducted full product evaluations of both the WD Red, and the Seagate NAS unit. Our consumer storage editor, Chris Ramseyer, also examined the performance of NAS RAID arrays.
Both NAS HDD's we are testing today have been geared specifically to provide acceptable performance in NAS units, but that will not always equate directly to the unbridled performance brought on by utilizing a standard RAID card in a DAS environment. There are higher-priced enterprise-class HDDs from both manufacturers (the WD SE, and the Enterprise Capacity (ES.3)), but many users find that the lower price point of NAS HDD's provide a more attractive solution. In many cases, the price difference can range from 30-50% when comparing entry-level enterprise HDDs with NAS units that can perform the same function.
When paired with a NAS unit, there are significant bottlenecks constraining the performance of the drives; namely the speed of the Ethernet connection. While Ethernet keeps speeds below 105 MB/s, the performance of these HDDs in a DAS environment can differ significantly.
RAID controllers have enhanced functionality; and not to mention large caches, which provide superior performance in comparison to off-the-shelf consumer NAS solutions. The first advantage is that file transfers from inside the server or desktop are much faster. RAID controller caches also catch small random write activity before it hits the drives, and then sequences the data to deliver superior write performance. This helps mitigate a significant performance disadvantage suffered by HDD RAID arrays, allowing the underlying RAID array to function efficiently.
Many users of DAS RAID arrays are typically professionals in video and audio editing, and those who require high-performance workstations. We also see this type of usage model bleed over to the SMB and SOHO space, where more powerful full-blown servers are utilized to provide enhanced functionality and security that isn't always available in a NAS unit. One notable weakness of many NAS units is the performance reduction when utilizing encryption. RAID controllers and server operating systems go a long way to mitigate that performance hit, while simultaneously providing enhanced management functionalities.
Using a RAID controller also provides enhanced RAID sets, and the mobility to move the array from computer to computer. RAID controllers also typically provide faster RAID rebuild times, and better performance when in a degraded state. While the advantages of utilizing a DAS solution are clear, the performance difference is not always as pronounced. Let's take a closer look.