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WD Red SA500 4TB NAS SATA SSD: features, specs and who it suits
A 4TB 2.5-inch SATA III solid state drive from Western Digital, designed for NAS use with speeds up to 560MB/s. What the specs mean and what to check.
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The WD Red SA500 is a 2.5-inch SATA solid state drive that Western Digital designed for network-attached storage (NAS). This model, WDS400T1R0A, offers 4TB of capacity. Because it is a standard SATA drive, it fits NAS bays and drive cages that take 2.5-inch drives, without needing an M.2 slot.
What makes it a NAS drive
A NAS stays powered on all day, serving files, backups and media to several devices. Western Digital says that, unlike standard SSDs, the WD Red SATA SSDs are designed and tested for 24/7 use. The brand highlights endurance, meaning the drive can handle the heavy read and write loads of a NAS, and it builds the drive with its own 3D NAND flash memory.
The listing also says the drive is purpose-built for NAS and aimed at both home and business users.
SATA III and 560MB/s
The interface is SATA III (6 Gb/s), which has a practical ceiling of roughly 550 to 600 MB/s. Western Digital lists speeds of up to 560 MB/s. That is much faster than a hard disk, whose sustained speeds are usually well below 300 MB/s, but slower than an NVMe SSD.
Inside a NAS, the network is often the limit. A gigabit connection carries around 110 MB/s, so a SATA SSD can already fill it. A faster connection, such as 2.5 or 10 gigabit Ethernet, lets you use more of the drive's speed.
Two ways to use it
As a cache: a NAS can use an SSD to hold frequently used data, so those files open quickly while the bulk of your data sits on hard disks. Western Digital describes the drive as optimized for caching in NAS systems, to access your most frequently used files quickly.
As storage: at 4TB, the drive can also hold a whole volume, for example for virtual machines, databases, photos or video editing projects. Western Digital lists OLTP databases, multi-user environments, photo rendering and 4K and 8K video editing as workloads where lower latency and better responsiveness help.
Some NAS models limit SSD use to caching, so check your NAS software.
Size and fit
The format is 2.5 inches and 7 mm thick, as the title states. The listed dimensions are about 3.9 x 2.8 x 0.3 inches, and it weighs around 0.1 lb. A 2.5-inch drive can go into a 3.5-inch bay with an adapter tray, though many NAS bays hold both sizes directly. Check your enclosure's drive tray for the screw layout.
Who it suits
It suits home users and small businesses who want fast, always-on storage in a NAS and have 2.5-inch SATA bays to fill. It is less useful in a system that has only M.2 slots, or when the main need is bulk capacity, where large hard disks are the usual route.
What to check before you buy
- Bay type: confirm your NAS has 2.5-inch SATA bays, or adapters.
- Compatibility list: check your NAS maker's list of supported drives.
- Network speed: a gigabit link limits how much of the drive's speed you can use.
- Cache or volume: see whether your NAS allows SSDs for both roles.
- Capacity: the stated 4TB uses 1TB = one trillion bytes, so reported space will be slightly lower.
- Backups: an SSD is not a backup. Keep another copy of important files.
The short version
- 4TB 2.5-inch, 7 mm SATA III SSD with speeds up to 560 MB/s.
- Designed and tested by Western Digital for 24/7 NAS use.
- Suits caching and fast storage volumes.
- Check bay type and NAS compatibility before buying.
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