WD Red SA500 4TB NAS SATA SSD: features, specs and who it suits

The WD Red SA500 4TB (model WDS400T2R0A) is a solid state drive from Western Digital made for network attached storage. It uses the 2.5-inch, 7mm SATA format, which fits the drive bays of many NAS enclosures. Western Digital designs the Red line for systems that run around the clock.

What "built for NAS" means

A NAS is a small always-on computer that stores and shares files on a network. Its drives run through long periods of reads and writes from several users at once. Western Digital says Red SSDs are designed for and tested in 24x7 conditions, unlike standard SSDs, and that their endurance handles the heavy read and write loads of a NAS. Endurance is usually rated in terabytes written (TBW), so check the datasheet for this model's figure and compare it with how much data you expect to write.

SATA III speed

The drive uses SATA III at 6 Gb/s, with speeds of up to 560 MB/s. That is the practical ceiling of the SATA interface, and it is far above what a hard disk delivers, particularly for small random reads. It's below what NVMe drives reach, but many NAS bays only support SATA. On a typical home network, the network link, such as Gigabit Ethernet at roughly 110 MB/s, is often the bottleneck before the drive is.

Caching in a NAS

Western Digital says the drive is optimised for caching, so that your most frequently used files can be reached rapidly. In a NAS with both hard drives and SSDs, an SSD cache holds popular data on the faster drive. Whether caching is available depends on the NAS model and its software, so check the manufacturer's documentation. The 4TB capacity also lets the drive work as plain storage in an all-SSD volume.

Workloads it targets

Western Digital says the drive reduces latency and improves responsiveness for OLTP databases, multi-user environments, photo rendering and 4K and 8K video editing. The common thread is many small, quick requests or several users at once, where an SSD's low latency helps more than raw sequential speed.

Form factors

The listing notes that the Red SA500 is available in 2.5-inch and M.2 form factors to fit slots in modern NAS systems. This product is the 2.5-inch, 7mm version. The 7mm height fits standard 2.5-inch bays, and mounting hardware or an adapter may be needed in a 3.5-inch bay. Check what your NAS needs.

Who it suits

It suits owners of a NAS with 2.5-inch SATA bays who want faster access to frequently used files, a small all-flash volume, or a quiet drive with no moving parts. It is less relevant to those who need NVMe speeds, or whose enclosure only has M.2 slots, where the M.2 version would be the match.

What to check before you buy

• Bay type: confirm your NAS has a 2.5-inch SATA bay, or the right adapter for a 3.5-inch one.
• Compatibility list: look at the NAS maker's list of supported drives and whether SSD caching is supported.
• Capacity plan: decide whether the drive will be a cache or hold data, and size it accordingly.
• Endurance: read the datasheet's TBW figure and compare it with your write workload.
• Network speed: check that your network can use the drive's speed, since a Gigabit link caps transfers.
• Backups: an SSD is not a backup, so keep copies of important data elsewhere.

The short version

• A 4TB 2.5-inch, 7mm SATA III SSD in Western Digital's Red line for NAS.
• Up to 560 MB/s, with Western Digital's 3D NAND.
• Designed and tested for 24x7 operation, with endurance for heavy read and write loads.
• Suited to caching and all-flash NAS volumes; check bay type and NAS support first.

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