Western Digital—a leader in HDD storage for not only NAS systems but all market segments—is expanding their SSD lineup with solid-state drives specifically optimized for NAS usage. Unlike mechanical HDDs, SSDs have nearly zero access latency, which improves access times far beyond what HDDs can achieve. NAS friendly SSDs are marketed as drives you use as the main storage device in your NAS. They can also be used as "hot-data" drives, in which the NAS operating system juggles frequently accessed data from the HDDs to the SSD for better responsiveness. A NAS-friendly SSD is typically designed for high uptime (near 24/7 operation) and offers higher endurance than ordinary consumer SSDs. They occupy a middle ground between the client and enterprise segments.

We previously reviewed the Seagate IronWolf 110 SSD, which seems to be the main competitor of the WD Red SA500 in terms of market positioning. Of course, both drives compete with every other SSD on the market, too.

Under the hood, the SA500 uses a Marvell 88SS1074 controller, which is an older model, but that doesn't have to be a bad thing. Considering the vast experience accumulated with this particular model and that it has been sold in huge quantities, all bugs should be ironed out, which is arguably more important in a NAS storage scenario than having the highest performance. Looking at our synthetic benchmarks, we see the SA500 excel in sequential workloads where speeds are capped by the transfer rates of the SATA 6 Gbps interface. Random reads are good, too. Where the drive falls behind, however, is random writes (despite having DRAM cache) and random mixed I/O (a write access is executed in parallel with a read access), which is an important scenario for a NAS system that has multiple users working with data at the same time. I'm not sure what the underlying reason is for the low mixed I/O performance. I reached out to WD in November, and over the course of the following three weeks WD asked for test configuration and system specs, but never got back to me with anything tangible in the end. The random IO shortcomings are clearly visible in our WinRAR real-life test, too, so they are not only of theoretical nature.

Overall, when averaged over all our real-life tests, we see the WD Red SA500 a few percent behind most SATA SSDs, but the differences are slim—only a few percentages. This won't be an issues when used in a NAS especially, as the networking connectivity and NAS hardware/OS will introduce additional bottlenecks. Compared to traditional HDDs, the differences will be huge, though, as transfer rates and seek times are an order of magnitude better. Seagate's IronWolf 110 NAS SSD is a bit faster than the WD Red, but costs more, too. An important metric for NAS performance is write-speed sustainability, and here, the SA500 scores big. No matter how much data you feed it with, write speeds will never budge. Some other SSDs have small TLC caches, which cause a significant loss in write performance once the cache is exhausted—no problem for the WD Red SA500.

With a price of $140 for the 1 TB version, the WD Red SA500 is priced quite reasonably, especially compared to the $200 Seagate IronWolf. For the higher price, the IronWolf does offer much higher endurance and data recovery services, but that might not matter for many who rather prefer a more affordable drive. Such a willingness to focus more on price could lure potential buyers to simply grab one of the super affordable 2.5" SATA drives out there ($100 for 1 TB), which can lead to significant cost savings in a NAS with many drive bays. On the other hand, most of these drives come neither with WD's five-year warranty or the extensive testing I'm sure WD has subjected the drive to. Another plus is the large capacity range spanning all the way up to 4 TB, which is important if you need a lot of storage capacity in your NAS. Overall, the WD Red SA500 is a very solid entry into the NAS-SSD market for WD that doesn't break the bank.