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Comparison Products
The Blue SN51000 must be understood within the context of Sandisk’s own SSD product stack. We’ve reviewed the Blue SN5000 – which uses QLC flash at 4TB – and the Black SN7100 within the last year or so. The SN5100 should perform better than the first, given by the model version, and below the second, given by the color branding. The Black SN7100 is a direct competitor of Samsung’s 990 EVO Plus, while the Blue SN5100 comes into a market that has quickly been dominated by the QLC-based Crucial P310. These are all good drives vying for roughly the same market, particularly for use in laptops.
The top DRAM-less controller in this segment is the Phison E27T, used by the P310 but also the TLC-based Sabrent Rocket 4. For higher capacities, the Maxio MAP1602 has also done quite well, and we are comparing the QLC-equipped TeamGroup MP44Q for that. SMI’s hardware has been far less common, but we have reviewed the Kingston NV3 – a drive that has various hardware configurations – with the SM2268XT2. Lastly, there is only one four-channel drive with DRAM: the popular Crucial T500.
Trace Testing — 3DMark Storage Benchmark
Built for gamers, 3DMark’s Storage Benchmark focuses on real-world gaming performance. Each round in this benchmark stresses storage based on gaming activities including loading games, saving progress, installing game files, and recording gameplay video streams. Future gaming benchmarks will be DirectStorage-inclusive and we also include notes about which drives may be future-proofed.
The Blue SN5100 finishes first in our 3DMark testing. This means it beats even the DRAM-equipped T500. This makes it a great choice for a secondary gaming drive, even over drives, like the 990 EVO Plus, that are often more expensive.
Trace Testing — PCMark 10 Storage Benchmark
PCMark 10 is a trace-based benchmark that uses a wide-ranging set of real-world traces from popular applications and everyday tasks to measure the performance of storage devices. The results are particularly useful when analyzing drives for their use as primary/boot storage devices and in work environments.
The Blue SN5100's PCMark performance is also excellent. It’s right up there with the T500 and P310. It should perform close to the Black SN7100, and it does, because both drives are using very similar hardware. In any pSLC mode – and most benchmarks fall into this category, as does the vast majority of real-world drive use – the drives should perform identically. If you’re using a drive as your primary boot device and tend to have that main drive very full, the results will likely differ from this. In that case, the SN7100, with TLC flash, would be the better choice, and that goes for the T500 with DRAM as well. The 990 EVO Plus is also a good choice for that over the QLC-based options. All three drives now come with a 4TB option, which reduces the QLC advantage.
It’s important to recognize that even though our results aren’t falsely optimistic, we do prepare the drives to get more realistic data before testing. There are many scenarios and edge cases where performance differences between drives will be different and more exaggerated. To condense that down, know your workloads and usage patterns, and apply that to our data. If your drive isn’t heavily used and is well-maintained, then the SN5100 will perform in the best of its class. If not, it may be lower on this list. That consideration must play into your purchase decision, as you can save a significant amount of money over the T500 for an effectively identical experience most of the time.
Console Testing — PlayStation 5 Transfers
The PlayStation 5 is capable of taking one additional PCIe 4.0 or faster SSD for extra game storage. While any PCIe 4.0 drive will technically work, Sony recommends drives that can deliver at least 5,500 MB/s of sequential read bandwidth for optimal performance. In our testing, PCIe 5.0 SSDs don’t bring much to the table and generally shouldn’t be used in the PS5, especially as they may require additional cooling. Check our Best PS5 SSDs article for more information.
Our testing utilizes the PS5’s internal storage test and manual read/write tests with over 192GB of data, both from and to the internal storage. Throttling is prevented where possible to see how each drive operates under ideal conditions. While game load times should not vary significantly from drive to drive, our results can indicate which drives may be more responsive over time.
The Blue SN5100 uses the PCIe 4.0 interface, making it a good choice for the PS5 (PCIe 5.0 SSDs are overkill for the PS5), as it hits that maximum bandwidth potential with plenty of performance under the hood. While QLC flash technically has higher latency than TLC, long-term reads will not come from the temporary pSLC cache; optimizations and software bottlenecks have made this moot. As you saw in our 3DMark and PCMark 10 sections, the Blue SN5100 is quite capable of being a responsive drive in normal situations. If this drive is priced right at higher capacities, we see it as an absolute win for console users, especially as the drive runs cool without any modification.
Transfer Rates — DiskBench
We use the DiskBench storage benchmarking tool to test file transfer performance with a custom, 50GB dataset. We write 31,227 files of various types, such as pictures, PDFs, and videos to the test drive, then make a copy of that data to a new folder, and follow up with a reading test of a newly-written 6.5GB zip file. This is a real world type workload that fits into the cache of most drives.
Our DiskBench testing gives a peek at read, write, and copy performance with a real-world file transfer. Due to how flash operates, reads will be faster than writes, so you can usually gauge the copy speed from just the write speed. Smaller transfers, including this 50GB dataset, will usually be fully in the pSLC cache, so the results here are under ideal circumstances. We have to mention that, as the Blue SN5100 is a QLC-based drive, and larger transfers with a fuller drive can and will copy more slowly.
With that out of the way, we see the T500 come out on top, with the Blue SN5100 impressively coming in second. It performs effectively the same as the Black SN7100, which is not surprising given that the two drives use very similar hardware. The T500 utilizes six-plane flash and features DRAM, making it difficult to beat here. The P310 uses the same generation of Micron flash, but in QLC with just four planes. BiCS8 is also a four-plane design, which may be one reason it has better latency, while Micron’s newest flash is more bandwidth-focused. This includes the newest QLC flash – we’re working on getting a Micron 2600 sample so we can better elaborate on this.
If you lean more towards latency and especially power efficiency, then the Blue SN5100 makes a lot of sense. It puts the P310 in its place, and the latency gap might only grow with Micron’s newer QLC flash. Then again, the 2600 has flexible caching, which breaks this discussion wide open once we get to PCIe 5.0. It’s just difficult to recommend the P310 over the Blue SN5100 at the same price when the latter is just better balanced in hardware in our opinion. That’s saying something because the P310 is already an immensely popular drive that hit all the right notes in our review.
Synthetic Testing — ATTO / CrystalDiskMark
ATTO and CrystalDiskMark (CDM) are free and easy-to-use storage benchmarking tools that SSD vendors commonly use to assign performance specifications to their products. Both of these tools give us insight into how each device handles different file sizes and at different queue depths for both sequential and random workloads.
The Blue SN5100 performs smoothly with only minor dips at 2MiB for read and write workloads in the ATTO benchmark. The Black SN7100, in comparison, retains its curve at the highest block sizes for reads. This could be due to differences in the QLC and TLC flash, respectively. We do have to point out that the P310, on the whole, is more consistent here, although it’s unlikely you will be transferring data at very specific sizes.
We’ve already seen in DiskBench that a real-world transfer favors the Blue SN5100. Moreover, at the typical 1MB block size in CrystalDiskMark, the Blue SN5100 offers excellent sequential performance regardless of queue depth. You will be able to eke out more with the Black SN7100’s TLC flash for writes, though. If we have to leave a caveat here, it’s this: we’re only looking at 2TB+ performance, and at lower capacities, the P310 should perform more favorably.
For latency, we see that BiCS8’s ability to be in a class of its own for QD1 random 4K reads carries over to the QLC version of the flash. It’s not as good as the TLC on the Black SN7100, but it’s darn good compared to the rest of the drives on this list. If this is the metric you care about most, then you can probably stop reading here and be satisfied in picking up one of the two WD drives. You would still have to read the entire review to see where to buy one over the other, though.
For write latency, we see these fall behind the P310, Rocket 4, and T500. The T500 is understandable as it’s using DRAM, and the Rocket 4 is using BiCS6 TLC flash with the excellent Phison E27T controller. The one result that might confuse is the P310, but we are reminded that Micron’s 232-Layer QLC flash on the drive is four-plane with optimizations for this kind of workload. Writes are usually in pSLC mode, so performance can be deceptive. To be fair to the P310, this result bolsters its application as a primary or singular drive, where frequent updates may be common. That said, we think any one of these drives would be adequate for everyday use.
Sustained Write Performance and Cache Recovery
Official write specifications are only part of the performance picture. Most SSDs implement a write cache, which is a fast area of pseudo-SLC (single-bit) programmed flash that absorbs incoming data. Sustained write speeds can suffer tremendously once the workload spills outside of the cache and into the "native" TLC (three-bit) or QLC (four-bit) flash. Performance can suffer even more if the drive is forced to fold, which is the process of migrating data out of the cache in order to free up space for further incoming data.
We use Iometer to hammer the SSD with sequential writes for 15 minutes to measure both the size of the write cache and performance after the cache is saturated. We also monitor cache recovery via multiple idle rounds. This process shows the performance of the drive in various states as well as the steady state write performance.
The Blue SN5100 uses Sandisk’s nCache 4.0 technology, which is also used in many of the most recent WD and Sandisk SSDs. This is a hybrid pSLC cache, meaning that the cache has both static and dynamic portions. This is similar to Samsung’s TurboWrite technology. The static portion lies outside of user space and is, as a result, is relatively small, but this cache is always available regardless of the amount of data stored on the drive. Being separate from the rest of the flash and cache, it provides a way to handle smaller and random writes in a portion of the drive that usually has much higher endurance. It also helps defer or combine writes in a way that reduces overall wear. The dynamic portion of the cache, on the other hand, will vary in size with the amount of data stored on the drive. The maximum cache size will also vary with overall drive capacity.
In our testing, the 2TB SKU of the Blue SN5100 was able to write at 6.45 GB/s for over 78 seconds. The cache is over 500GB, which is close to the maximum amount possible for a 2TB drive of QLC flash. QLC flash operates in a 4-bit mode, while the pSLC cache operates in a 1-bit mode; therefore, the cache is necessarily at most one-quarter the size of all flash.
The full amount of flash on a drive is more than is available to the user, and there must be accounting for the decimal versus binary capacity discrepancy. It’s likely that having a static portion for caching reduces the amount available for the dynamic portion, in part because the controller does need extra space for system functions and to have free blocks for future writes. Sandisk also appears capable of performing some magic with caching, given the Black SN8100's high steady-state write performance.
If, for some reason, you exhaust the cache, the drive is then forced to write directly to the QLC flash and/or will hit a slower folding state where it must wait for flash to be moved over from the cache in order to free up needed space. This yields a steady state write rate of 442 MB/s, which is low but not bad for QLC flash. The other QLC-based drives in our test did worse, including the P310, except for the Blue SN5000, which has more dies to work with at 4TB. The Black SN7100 is less than double the Blue SN5100’s speed, but we don’t know the raw difference in flash speed. Usually, TLC flash is about 2.5 to 3 times faster than QLC, but both of these drives are using very large caches and are no doubt tuned differently than the eight-channel, DRAM-equipped Black SN8100.
To bring things back into focus: this drive is slow when the cache is full, but it’s still fast enough to hang with SATA SSDs. You shouldn’t really be getting to that point with a budget drive. However, if you care about sustained performance, there are many better drives available. You always want to be looking for TLC flash in that case, and usually smaller caches. The Crucial P510 is almost a perfect example, even though it’s four-channel and DRAM-less. You want DRAM and eight channels for the heaviest tasks. That’s not the audience for the Blue SN5100, though. This drive is made for light use, for laptops, as a gaming drive, etc. It has enough performance here for that, even in suboptimal conditions.
Power Consumption and Temperature
We use the Quarch HD Programmable Power Module to gain a deeper understanding of power characteristics. Idle power consumption is an important aspect to consider, especially if you're looking for a laptop upgrade as even the best ultrabooks can have mediocre stock storage. Desktops may be more performance-oriented with less support for power-saving features, so we show the worst-case.
Some SSDs can consume watts of power at idle while better-suited ones sip just milliwatts. Average workload power consumption and max consumption are two other aspects of power consumption but performance-per-watt, or efficiency, is more important. A drive might consume more power during any given workload, but accomplishing a task faster allows the drive to drop into an idle state more quickly, ultimately saving energy.
For temperature recording we currently poll the drive’s primary composite sensor during testing with a ~22°C ambient. Our testing is rigorous enough to heat the drive to a realistic ceiling temperature.
One thing we want to get out of the way before we dig into the data: we’ve listed Sandisk’s official power numbers in our table on the first page of the review. This is something we may continue to do moving forward with datasheets that indicate this information. Generally, we prefer to look at our real-world results, but in this case, Sandisk lists both read and write average power use – 4.1W for each on the 2TB. Our write-heavy testing peaked at 4.12W with an average of around 3W. As far as we’re concerned, that means Sandisk is bang-on with their data. The S.M.A.R.T. reading indicates the drive can peak up to 5W, but this information is not always reliable, and we tend to measure peaks at a more realistic value.
The Blue SN5100 is, as expected, fantastically power-efficient. There’s no question this drive is a great choice if you are at all worried about power draw or thermal output. The controller in use here is not the most efficient design on paper, but Sandisk’s ability to tune it for a specific purpose makes for a great pairing with the very power-efficient BiCS8 flash. This flash isn’t running full bore, and this is a PCIe 4.0 drive, so that does help to some degree, but PCIe 5.0 drives can finish our workload faster and do quite well. Consider that the Sandisk WD Black SN8100 is on par in power efficiency with the Blue SN5100. This demonstrates how effective optimization can be when you tune with scalable hardware.
Our test bench will run cooler than many systems – the ambient would be higher with heavy CPU and GPU loads in an enclosed case, depending on the cooling solution – but it’s still a predictable way to compare different drives. The Blue SN5100 hit a maximum temperature of 53°C during our write test, which is approximately 37°C below the serious throttling point. This drive is simply a gold mine for laptop and HTPC users, and for full-length capable portable computer systems users. Many, if not most, of these are still running PCIe 4.0 slots will have read-heavy workloads, which favors QLC flash just fine. This might be better as a secondary drive for a serious desktop PC build, though.
Test Bench and Testing Notes
CPU | Row 0 - Cell 2 | |
Motherboard | Row 1 - Cell 2 | |
Memory | Row 2 - Cell 2 | |
Graphics | Intel Iris Xe UHD Graphics 770 | Row 3 - Cell 2 |
CPU Cooling | Row 4 - Cell 2 | |
Case | Row 5 - Cell 2 | |
Power Supply | Row 6 - Cell 2 | |
OS Storage | Row 7 - Cell 2 | |
Operating System | Row 8 - Cell 2 |
We use an Alder Lake platform with most background applications such as indexing, Windows updates, and anti-virus disabled in the OS to reduce run-to-run variability. Each SSD is prefilled to 50% capacity and tested as a secondary device. Unless noted, we use active cooling for all SSDs.
Sandisk WD Blue SN5100 Bottom Line
It wasn’t that long ago that we gave the Crucial P310 a 4/5 star rating, which is exceptional for a budget-oriented, QLC-based SSD. We do judge drives both relatively and absolutely, which means that sometimes the score may seem out of place. The Blue SN5100 is one such situation where it feels better than the P310 on the whole, but nothing in its DNA screams that it’s a 4.5 drive. One reason for this is that the Blue SN5100 right now is priced far too high to make it competitive with the fast-selling P310. Another reason is that you have the Black SN7100 with TLC flash at a very good price. We gave that drive a 3/5 because its performance was frankly last-gen, but in lieu of the price trends that came after – with QLC flash especially being less competitive – you could put it above the P310 and Blue SN5100.
On the other hand, the Blue SN5100 often performs above its weight class and gives the Black SN7100 a run for its money. At an appropriate price point, it simply is the better drive. Most users will never experience its slowest state – which, to be honest, isn’t even that bad – and it’s one cool customer. You can integrate it into any system and expect good results without needing to adjust cooling or other settings. That’s also true of the Black SN7100, but we feel that the Blue SN5100 is a better fit for its specific market segment. It’s a great secondary or game drive at up to 4TB, and when the pricing is corrected – WD and Sandisk have been aggressive here recently – it should deliver an experience equal to the Black SN7100 at a lower price. That’s why this drive gets a higher score.
If you want TLC flash, you would go with the Black SN7100, right? Well, frankly, there are better TLC-based drives like the Rocket 4 if you actually are worried about sustained write performance, for instance. The Black SN7100’s greatest strength is its power efficiency, which is great for laptops but less meaningful in desktops. Its saving grace is that it’s priced so aggressively. On an even field, it’s simply an average drive overall. And the market agrees with us because not only is Crucial’s P310 selling well, but there is a history of “cheap” drives selling well going back to the P3 Plus and the P2 before that. People want inexpensive drives. We think the P310 delivers on that, but if prices are equal, we would favor the Blue SN5100, so take that into consideration.
If you want this general range of performance with power efficiency but demand DRAM, then the Crucial T500 remains the way to go. It has some issues with sustained writes, which, if important to you, means you should consider something more high-end, such as the WD Black SN850X or Samsung 990 Pro. Drives based on Phison’s E18 also apply, but recent reports of firmware-caused sluggishness persist. The good news is that Phison has fixed firmware coming to its drives. If you’re looking the other way to even cheaper drives, then there are still mid-range champions like the WD Black SN770 and Blue SN5000, but they must be less expensive to make sense. Many other drives in that segment have varying hardware, which can be unpredictable.
Aside from competing for a spot on our Best SSDs list, we can confidently state that the Blue SN5100 is impressive on its own. BiCS8 flash continues to exceed our expectations in performance, especially latency, and power efficiency alike. Sandisk’s controllers also remain well-optimized and reliable. This is the perfect type of QLC-based drive you could ask for, without any real weaknesses. Even the caching is pretty solid. Our only real complaint is price. This drive has to come back down to earth. If it can do that, then we can highly recommend it as the best in its class.
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