SanDisk G-RAID Mirror review: Fast, safe hard drive storage and lots of it

WD’s G-RAID Mirror is an external enclosure housing two 3.5-inch hard drives. It provides up to 48TB of storage with the drives in striped (RAID 0) mode, or half that in mirror mode RAID 1. It also provides a Pro Blade SSD port for SanDisk’s modular NVMe SSDs.

What you may not realize if you haven’t been around a 3.5-inch HDD in a while: They’re a whole lot faster than they used to be. In RAID 0, the G-RAID Mirror can deliver data at over 400MBps. This is not your father’s RAID box.

Further reading: See our roundup of the best external drives to learn about competing products.

G-RAID Mirror features

The G-RAID Mirror is a handsome, dark gray, Thunderbolt 3, two-drive external enclosure available in capacities up to 48TB/24TB (striped/mirrored). The unit measures 5.24 x 8.27 x 4.06 inches (13.30 x 21.00 x 10.21 centimeters). It can weigh up to 7 pounds (3.17 kilograms) depending on the drives inside. Standing on non-skid feet, there’s little chance of this drive dancing around the desktop. The four hex bolts on each side hide anchor points for attaching the unit to a Digital Imaging Technician cart or adding other hardware.

The back of the G-RAID Mirror is home to two Thunderbolt 3 ports (1 computer, 1 pass-through, see below) as well as the RAID configuration double dip switch (JBOD, RAID 0/1). That means the RAID is onboard, which I prefer over the software variety as it’s portable across operating systems without installing said software. There’s also a button to adjust the front LED light.

The front of the drive is home to only the aforementioned LED light, and the removable front grate that allows access to the hard drives for upgrade or replacement. Note that because of the fantastic amount of capacity, rebuilding a RAID 1 array can take a very long time — two hours per terabyte.

By far the most unusual feature of the G-RAID Mirror is its Pro-Blade Transport slot. The somewhat pricey Pro-Blade Transport modules are NVMe SSDs in proprietary enclosures that slide into the slot. They’re super handy for uploading, offloading, and backup, and are fast enough that you could boot from them. However, the Pro Blade system is 20Gbps USB 3.2×2, and current Thunderbolt (Mac and Windows) implementations don’t support USB 3.2×2 at 20Gbps, dropping it to 10Gbps. Still fast, but not optimal. Thunderbolt 3/4 does support 20Gbps USB 4, though, so I’m confused as to why SanDisk didn’t choose USB 4 for the Pro-Blade Transport, or even Thunderbolt 3. Especially as Mac users seem to be the intended audience.

As this drive is largely aimed at the Apple/video production crowd, the G-RAID Mirror ships formatted to APFS. A single 24TB RAID 1 volume was in our test unit’s case. There is no software on the drive as you’ll find with most 2.5-inch hard drives.

The high-capacity HDD conundrum

While external 3.5-inch hard drives can be ultra capacious (trust me, it’s a hoot to see a 48TB drive on your desktop), holding so much more data than other media also makes them difficult to back up. The only media of acceptable speed capable of holding the same amount of data is, yup, another hard drive. Consequently, the easiest way to avoid data loss from hard drive failure is mirroring it to another hard drive (RAID 1), or split it among multiple hard drives in another type of fault tolerant RAID.

How you set the G-RAID Mirror will depend on whether it’s a primary or secondary repository. If it’s just one component in a larger storage scheme, and backed up (macOS RAID for instance), then running it at full-capacity striped RAID 0 is fine. However, if it’s a solo repository, you’ll want to run it at half-capacity, mirrored RAID 1.

Alas, mirroring tends to kill a hard drive’s price advantage over the far faster, far more physically robust, and more reliable SSDs. Not entirely, but the difference is drastically reduced. A handy segue into…

How much does the G-RAID Mirror cost?

The G-RAID Mirror is available in (striped/mirrored) 12TB/6TB, 16TB/8TB, 24TB/12TB, 36TB/18TB, 44TB/22TB, 48TB/24TB capacities for $660, $750, $1,000, $1,200, $1,400, and $1,600, respectively, in the U.S. Part of the reason for the higher-than-normal pricing is the Thunderbolt 3 connectivity.

That works out to $55/$110, $46.88/$93.76, $41.67/$83.33, $33.33/$66.66, $31.82/$63.64, $33.33/$66.66 (striped/mirrored) per terabyte. As you can see, the 44TB unit is the sweet spot in terms of price per terabyte.

Last we checked, 4TB and smaller SSDs were down to around $70 per terabyte, though the larger 8TB models were still over $100 per TB. Keep that in mind when deciding on your storage plan of attack.

If you’re not interested in the current Pro Blade system, then a cheaper USB 3.x RAID enclosure such as the WD (SanDisk’s owner) MyBook Duo is an option.

How does theG-RAID Mirror perform?

The 48TB G-RAID Mirror that SanDisk sent me arrived configured in RAID 1 (mirroring) — as you’d expect given the name. I tested it in that mode, as well as in RAID 0 to see just what it’s capable of. (Spoiler alert: a lot more.) I also tested the Pro Blade as I had two modules on hand, and put all three through PCWorld’s test suite for good measure.

The result of all these tests means there are a lot of captures and images to wade through below. If you want to avoid that, the summary is that sequential throughput with the hard drives is between 175MBps and 210MBps in RAID 1, and 350MBps and 410MBps in RAID 0.

The Pro Blade reads and writes around 800MBps, well below the 1.8GBps it manages over USB 3.2×2 on a Windows PC. In practical terms, however, even the HDDs in RAID 1 are fast enough for at least an 8K video stream, and probably several. With the Pro Blade on board, which mounts as a separate drive, you can accommodate even higher bandwidth scenarios.

Sustained throughput is much better than with external 2.5-inch hard drives, especially in RAID 0. However, as you’ll see, if you want fast seek times, these are not the drives you seek.

As I said, it’s always nice to have a little context, so we’ve included the results from PCWorld’s Windows test bed for the hard disks in both RAID 0 and RAID 1, as well as the Pro Blade SSD. They’re compared to the recently reviewed Seagate Expansion Desktop hard drive, and the Pro Blade Transport using USB 3.2×2.

Yes, the numbers are a bit more impressive under Windows. But again, the Thunderbolt hindered the Pro Blade on the G-RAID by limiting it to 10Gbps.

The random numbers for the hard disks are minuscule compared to the Pro Blade’s. But CrystalDiskMark 8’s numbers are still valid, even if it’s not designed specifically for HDDs.

Again, the Pro Blade Transport’s results are included to show you what these modules can do at 20Gbps on a real 3.2×2 bus, and just how choked the Pro Blade on the G-RAID Mirror is by the Thunderbolt 3 bus.

The results for the Transport on the Mac are identical to those for the port embedded on the G-RAID Mirror.

Obviously, once again, the G-RAID Mirror in RAID 0 was way faster writing 450GB than RAID 1.

The G-RAID Mirror’s fan, when it kicks in at startup is rather loud. Most of the time, however, my Mac Studio fan makes as much noise, and that’s hardly any. To be fair, my office has test beds and NAS boxes whirring away most of the time, so my tolerance for white noise is very high. But there’s also noise due the read/write heads moving about. If you haven’t been around hard drives for a while, it might bug you. One might argue for more sound-deadening material inside, but that tends to trap heat as well noise, and that would be bad.

Note that the user guide I downloaded says you only have to turn off the G-RAID Mirror twice when changing RAID modes, which one might interpret as using the power button. This would be wrong. Info on the website and my experience says you must pull the power plug both times to switch RAID modes.

In total, the G-RAID Mirror is a lot faster in RAID 0 than RAID 1, which means you might be better off with two less capacious models using RAID 0 and macOS’s own RAID 1 mode. Then again, you could employ the Pro Blade when you need real speed, and leave the HDDs safely mirrored.