Sandisk WD Blue SN5100 2TB SSD Review: A Rhapsody in Blue

Thanks to the performance we see with the Sandisk WD Blue SN5100, the market now has not just one great QLC SSD, but two great QLC SSDs. This turn of events was unfathomable a generation of drives ago, but the components are now mature enough to offer great value for everyday users and storage enthusiasts alike. We were first impressed by Crucial's P310, but the Blue SN5100 has quietly come along to redefine what a QLC drive can do.

Sandisk has followed up on the excellent Black SN7100 and SN8100 with another compelling mid-range Blue drive, bumping performance up from the SN5000. The Blue drives have always been a popular and inexpensive option, but in some cases, the different models felt overlapping, even with some of the lower-end Black drives, such as the SN770. It’s almost too much of a good thing. Now, with the SN5100 coming in hot with QLC flash, which the previous SN5000 only used at 4TB, we have a drive designed for everyone.

All of WD’s and Sandisk’s many Blue NVMe SSDs have been good budget performers to the point that it sometimes gets confusing to discern one from another; the controllers and flash used are scalable in that way. The Blue SN5100 carries on with this tradition, but it’s also marking the full transition from TLC to QLC flash. This might horrify some people, but the fact is, this drive performs well for 99% of typical users. You’d have difficulty in a blind taste test between this and the TLC-equipped Black SN7100, and if Sandisk can get the price down to an appropriate level, that’s a very attractive reality.

We still prefer the Blue SN5100 as a secondary or game-focused drive, or perhaps as a budget laptop upgrade drive, but we think it’s to the point that this drive could work anywhere. It feels like it could replace low-end TLC options without issue. There’s something about this drive that puts it ahead of the pack in comparison to some of the older QLC drives, mostly due to the flash. It’s power-efficient and has excellent latency, which makes it feel like a high-end drive a lot of the time. It’s a shame that QLC flash isn’t holding its discount due to enterprise demand because this drive at an optimal price level would be nearly unbeatable. It’s still a drive worth keeping an eye on.

Sandisk WD Blue SN5100 Specifications

The Sandisk WD Blue SN5100 is available in 500GB, 1TB, 2TB, and 4TB capacities. QLC flash can be tricky at lower capacities like 500GB, as there are fewer dies with which to interleave. Performance on this drive is best at 1TB and 2TB, but there will be much interest in the 4TB. The drive can hit up to 7,100 / 6,700 MB/s for sequential reads and writes and up to 1,000K / 1,300K random read and write IOPS.

Pricing at the time of the review was a problem, though, at $54.99, $79.98, and $142.99 for the smaller SKUs. The Sandisk WD Black SN7100 is, in fact, less expensive and, with TLC flash, is the better drive. In fact, that model is an excellent value all around. We suspect the Blue SN5100 will be adjusted below that pricing – that’s the only way the Blue and Black monikers make sense relative to one another — which would make it potentially a fantastic budget SSD.

Sandisk backs the drive with a standard five-year warranty and up to 600TB of writes per TB capacity. QLC flash tends to be rated for only about half the program/erase cycles as comparable TLC, but even then the endurance is sufficient for this many writes. Usually but not always QLC drives will have lower TBW but Sandisk didn't hold back here. This does not reflect actual NAND flash endurance, but rather the TBW is chosen for warranty purposes. This drive isn’t supposed to be beaten up with tons of writes, and enterprise-like workloads can and will wear the flash worse than normal consumer usage. We don’t think this write limit holds back the drive for its intended purpose in any way.

Sandisk WD Blue SN5100 Software and Accessories

Sandisk has two downloads for its SSDs: the SanDisk Dashboard and Acronis True Image. The former is an SSD Toolbox application previously known as the WD Dashboard – if you see that in our past reviews, know that the new dashboard covers both WD and Sandisk SSDs. This dashboard is roughly on par with Samsung’s Magician and is useful for a range of things. Aside from letting you update the drive’s firmware, it also allows you to check and monitor drive health and engage features such as TRIM and secure erase. This application is only for Windows, but True Image also works on macOS. True Image is designed for backups and imaging to protect your data when switching drives, which is always a useful feature.

Sandisk WD Blue SN5100: A Closer Look

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The Blue SN5100 is single-sided with a single NAND flash chip, power management circuitry, and a DRAM-less controller. This drive would work in a shorter form factor. The drive does have a QR code PSID, but it is otherwise uninteresting.

A 4TB SKU is on the way and is also single-sided. With current technology, such a drive would have two NAND flash packages with the standard 1Tb dies, but could theoretically get away with just one with 2Tb dies. There is a performance dip for the 4TB models, according to the datasheet, which would be either from extra memory addressing overhead with the latter solution or an abundance of dies in the former. WD could also choose to use 2Tb dies with two NAND flash packages to take advantage of better yields. One reason to stick with a single package is if there is intent for shorter form factors in an OEM counterpart, particularly as such drives tend to be single-sided.

The Sandisk WD Black SN7100 and Sandisk WD Black SN8100 use the TLC version of this flash and show no performance loss at their maximum capacities at the time of our reviews, but we know the controllers are able to handle that many 1Tb dies without an issue. The Black SN7100 has been updated with a 4TB SKU post-review, which does exhibit a similar performance drop as the SN5100, and in that case, it’s due to the use of so many 1Tb dies. To condense this into something understandable: you are going to see some level of performance loss at the highest capacity of these drives. That may impact the upcoming 8TB Black SN8100 as well, unless Sandisk has a trick up its sleeve. This was avoided with the 8TB WD Black SN850X, which utilized newer, denser flash, a strategy later adopted by Samsung with the 4TB 990 Pro.

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The A101-000103-A1 is a proprietary controller from Sandisk that is also used on the WD Blue SN5000. This is a simple four-channel DRAM-less controller made to optimally run with 16 dies at 2400 MT/s, which translates to 2TB at 7+ GB/s. BiCS8 is rated for up to 3,600 MT/s, but this is not needed for PCIe 4.0. For PCIe 5.0, this flash with a similar controller, like the Phison E31T, can hit up to at least 10 GB/s. There are advantages other than bandwidth for running at a higher I/O speed, such as slightly better latency. However, running at a lower clock is more power-efficient. The Black SN7100 demonstrates this well by having the best power efficiency we’ve seen to date.

The Blue SN5100 differs from the Black SN7100 by its use of QLC rather than TLC flash. In practice, this isn’t as big a deal as it sounds. In pSLC mode, the flash will perform similarly, and QLC often has optimizations for reads, which might come from native flash. You might never notice a difference between the two. QLC flash does have lower endurance with approximately half the rated amount, depending on the flash and quality, but this is still an immense amount of writes that 99% of users won’t ever hit. Nevertheless, performance concerns do remain for the worst-case, which cannot be denied. We cover this in our write saturation test.

QLC flash should be more affordable as a trade-off, but this often has not been the case. One reason is that enterprise demand for QLC flash is higher than ever to handle large data with far better response times than a mechanical HDD provides. This has gotten worse with the AI and LLM booms, especially considering that the YMTC flash, which could alleviate this shortfall to some degree, has been politically problematic for the U.S.

Most inexpensive 4TB drives with QLC use YMTC flash, in fact, while Micron is holding back its QLC for enterprise and its own drives. That would include the Crucial P310 and the OEM Micron 2600. Historically, BiCS has not made a big splash with QLC flash and has been mostly only available in TLC. This completely changes with the Blue SN5100 as a follow-up to the Blue SN5000.

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