Samsung is the biggest producer of flash memory in the world—by a fair margin. The latest numbers from IHS iSuppli peg Samsung’s share of the NAND market at over 42%, well ahead of Toshiba’s at 25% and Micron’s at 21%. Given those figures, it’s no surprise Samsung is also one of the biggest players in the SSD business.
What may surprise you is just how long Samsung has been one of the top dogs in that realm. Everyone’s familiar with the 830 Series, which debuted a little more than a year ago and quickly became one of the most desired SSDs among PC enthusiasts. The 830 Series was a follow-up to the 470 Series, which didn’t make as big of a splash in hobbyist circles. Samsung had other SSDs before that, but I bet you can’t name any of them.
I’m sure you can list a few major PC makers, though. Samsung claims it’s been the number-one supplier of SSDs to the big-name PC brands since 2006, a full two years before Intel’s first SSD even hit the market.
With the PC establishment seemingly sewn up, Samsung has increasingly targeted customers who buy drives one at a time rather than in lots of a thousand. The size of this market is growing as SSDs become more affordable for upgraders and system builders. Right now, the sweet spot is around $200, where there are numerous drives in the 240-256GB range. One of those options is Samsung’s next-generation 840 Series SSD.
While the name suggests this drive is a successor to the 830 Series, the new model isn’t quite a direct heir. Yes, the controller has been updated and the NAND is built using a smaller fabrication process. However, Samsung has traded the 830 Series’ MLC flash for TLC chips that squeeze an extra bit into each cell. This NAND costs less per gigabyte, which is probably why the 840 Series 250GB rings in at just $180 right now. The implications of that extra bit go beyond pricing, affecting not only the drive’s performance, but also its longevity. Let’s take a closer look.
The skinny on TLC
TLC NAND is the defining characteristic of the Samsung 840 Series. Thankfully, I can assure you it has nothing to do with the television network responsible for spawning Here Comes Honey Boo Boo. TLC stands for “triple-level cell” and describes the number of bits (three) stored in each flash cell. The MLC NAND commonly found in consumer-grade SSDs packs two bits per cell, while the SLC flash reserved for uber-expensive server drives has only one bit.
More bits per cell translate to more gigabytes per die, which in turn means more gigabytes per wafer. MLC doubles the storage capacity of SLC, and TLC adds 50% on top of that. By adding bits, the capacity of each wafer can be increased without shrinking the fabrication process.
TLC NAND isn’t a new technology; flash makers have been cranking out it for years. The triple-stuffed NAND has mostly been confined to devices like thumb drives because its endurance and performance haven’t measured up to MLC NAND. For a sense of why that is, it helps to have an understanding of how data is stored in flash memory. Behold my crudely drawn flash cell diagram:
Each flash cell consists of insulated control and floating gates situated above a silicon substrate. If enough voltage is applied to the control gate, electrons will rise up from the substrate and into the floating gate through a process called tunneling. When the voltage to the control gate is cut, the oxide insulator traps the migratory electrons in the floating gate. The presence of those electrons creates a negative charge that changes the threshold voltage required to activate the cell, effectively writing data to it. Applying a sufficiently strong negative charge to the substrate reverses the process, causing electrons in the floating gate to return to the substrate. This mass exodus erases the cell and returns the threshold voltage to its lowest state.
Because there’s some variation in the characteristics of individual cells, any data that’s written needs to be read for verification. Data is read by asserting a voltage at the control gate and checking for current flow between the source and the drain. Current will flow if the control voltage is higher than the threshold voltage of the cell.
Reading and writing SLC NAND is fairly quick because there are only two values to consider: 0 and 1. Additional control voltages must be applied to account for the 00, 01, 10, and 11 values supported by MLC NAND, and that takes more time. The process is even longer with TLC flash, which can store eight different values between 000 and 111, requiring more control-voltage levels.
Dealing with TLC flash becomes even more challenging as the NAND starts to wear out. Electrons tunneling through the oxide layer can break down the bonds in the insulator and become trapped. The negative charge created by these stranded electrons raises the minimum threshold voltage required to activate the cell, narrowing the voltage range that can be used for programming. The more values that are crammed within that shrinking voltage range, the more difficult it is to distinguish between them. That’s why TLC NAND typically tolerates fewer write-erase cycles than MLC flash, which is itself less durable than SLC NAND. Eventually, the tunneling oxide degrades to the point where the cell is no longer viable and has to be retired.
Transitioning to finer fabrication nodes reduces NAND longevity even further because the layer of tunneling oxide gets thinner as the cell geometry shrinks. That detail is particularly important for the Samsung 840 Series, whose TLC chips are fabbed on a next-gen 21-nm process. The 830 Series uses 27-nm NAND.
Should you be concerned? Maybe. Unlike some SSD makers, Samsung doesn’t quote endurance ratings on its website or in the official Reviewer’s Guide attached to the 840 Series. We’ve asked the firm on multiple occasions to characterize the drive’s endurance, in terms of either the number of write-erase cycles the NAND can survive or the total volume of writes the drive can withstand as a whole, and we’re still waiting for a response.
To its credit, Samsung covers the 840 Series with the same three-year warranty that applies to the 830 Series. The firm also says the NAND rolling off its production lines is sorted, and that only the highest quality chips are used in its SSDs. We’ve already seen Intel cherry pick high-endurance MLC NAND for enterprise-oriented drives that would have otherwise used SLC memory. Samsung appears to be doing something similar with TLC memory and consumer SSDs. Given how popular MLC-based offerings have become with the server crowd, we’re not inclined to write off the 840 Series due solely to its use of TLC NAND.
The rest of the 840 Series SSD
There’s more to Samsung’s 840 Series SSD than its 21-nm TLC NAND. Heck, there’s more to the NAND than the fab process and the number of bits per cell. Like the last two generations of Samsung SSDs, the 840 Series’ flash memory conforms to the Toggle DDR NAND specification. This standard was jointly developed with Toshiba and is an alternative to the ONFI flash spec backed by Intel, Micron, and Hynix.
Toggle DDR is capable of executing reads and writes on both the rising and falling edges of a data strobe, hence the DDR moniker. Synchronous ONFI NAND has a similar double data rate driven by an external clock cycle. That external clock is always running, while Toggle DDR turns on its data strobe only when transfers are taking place. As a result, Toggle DDR chips should be more power-efficient at idle than their ONFI counterparts. We’ll put that notion to the test a little later in the review when we probe the 840 Series’ power consumption.
Although Samsung has equipped its SSDs with Toggle DDR NAND for a couple of years, the 840 Series is the first to use flash chips compliant with version 2.0 of the Toggle standard. The initial spec allowed for transfer rates up to 133 MT/s, a ceiling that’s been bumped up to 400 MT/s for Toggle DDR2. That 400 MT/s limit nicely matches the maximum data rate of the ONFI 3.0 specification, by the way.
To support the 840 Series’ faster NAND, Samsung has cooked up a new revision of its proprietary, triple-core SSD controller. Like the 830 Series’ MCX controller, this new MDX chip has eight memory channels and ARM9-based processor cores. Multiple cores are used to prevent background tasks like garbage collection from slowing the drive’s performance with user workloads. The firmware controls which tasks are assigned to the individual cores, and there’s some flexibility to shuffle the load around.
Samsung always makes a point of highlighting the fact that its controller technology doesn’t use SandForce-style write compression. A little compression mojo might not be a bad idea given the inherent endurance handicap associated with 21-nm TLC NAND, though. Compression allows fewer blocks to be written to the NAND, reducing the write amplification factor and leaving more write-erase cycles in reserve. This approach biases performance toward easily compressible data, but there are ways to reduce the write amplification factor without resorting to compression. SSDs can also wring more life out of their NAND with smarter error correction and signal processing algorithms. Alas, we couldn’t pry any specifics from Samsung regarding its use of those techniques.
We do, however, know that the 840 Series attempts to extend its lifespan by reserving more NAND capacity as spare area available only to the controller. The drive’s 120, 250, and 500GB capacities are a bit lower than the 128, 256, and 512GB you might recall from the 830 Series.
Lower capacities usually hint at the presence of RAID-like schemes that protect against physical flash failures. The 840 Series doesn’t arrange its NAND in a redundant array, though. Samsung restricts NAND-level redundancy to its enterprise-grade drives. It does, however, endow the 840 Series with full-disk encryption support.
Despite the fact that the 840 Series is aimed at the mainstream market, the family doesn’t include anything below 120GB. Perhaps that’s because the base model’s street price is already quite low, at just $100.
If you think that’s low, check out the sequential write speed ratings for the various members of the 840 Series lineup.
|Capacity||Max sequential (MB/s)||4KB random (IOps)||Price|
Ouch. The 250GB model’s 240MB/s maximum sequential write speed doesn’t inspire confidence. To put it in perspective, consider that the old Samsung 830 Series 256GB is rated for 400MB/s sequential writes. That drive has the same write speed rating as its 512GB sibling, but there’s a sizable gap between the 250 and 500GB versions of the 840 Series. I suspect the larger 840 Series drive uses a greater number of NAND dies, allowing it to exploit more parallelism within the controller. We’ve asked Samsung to reveal the size and number of NAND dies for each member of the 840 Series but are still awaiting an answer.
For what it’s worth, the performance of contemporary MLC SSDs tends to plateau at around 256GB. TLC NAND can serve the same capacity with fewer dies, but it looks like the 840 Series 250GB doesn’t have enough dies to take full advantage of the controller.
Of course, the NAND dies aren’t the only memory chips onboard the 840 Series. The drive features DRAM cache memory used primarily to store lookup tables. This low-power DDR2 cache also serves as a landing pad for some incoming host writes. The 120GB model has a 256MB cache, while the higher-capacity flavors sport 512MB.
We’d love to show you a gratuitous close-up of the 840 Series’ DRAM cache and other chips, but Samsung has locked down the case with pentalobe screws straight out of Apple’s playbook. (We’re in the process of obtaining the tool required to crack open the case.) In some ways, the drive bears an eerie resemblance to the iPhone 5. The case is black; it’s rectangular with rounded corners; and a chamfered edge runs around the rim. At just 7 mm thick, the 840 Series should be slim enough for Apple, too—and for folks looking to upgrade thinner notebooks that can’t accommodate the 9.5-mm cases that house most SSDs.
Speaking of upgrades, the SSD Magician utility that accompanies Samsung SSDs is one of the best around. There’s secure-erase functionality, of course, plus optimization routines and a built-in benchmark. The integrated flashing utility can reach out and grab updates directly from Samsung, and the overprovisioning can be tweaked to allocate more NAND capacity as spare area. Don’t get too excited about that cloning icon, though. It refers to a copy of Norton Ghost 15 that’s included only with drives sold as part of upgrade kits.
If you want to keep tabs on the health of the 840 Series’ TLC NAND, drilling down in the System Information section of the interface reveals an estimated lifetime display based on SMART data. After hammering our drive with several days of testing, the needle remains close to 100%. Speaking of testing, it’s time to see how this puppy performs.
Our testing methods
If you’re familiar with our test methods and hardware, the rest of this page is filled with nerdy details you already know; feel free to skip ahead to the benchmark results. For the rest of you, we’ve summarized the essential characteristics of all the drives we’ve tested in the table below. Our collection of SSDs includes representatives based on the most popular SSD configurations on the market right now.
|Corsair Force Series 3 240GB||6Gbps||NA||SandForce SF-2281||25nm Micron async MLC|
|Corsair Force Series GT 240GB||6GBps||NA||SandForce SF-2281||25nm Intel sync MLC|
|Corsair Neutron 240GB||6GBps||256MB||LAMD LM87800||25nm Micron sync MLC|
|Corsair Neutron GTX 240GB||6GBps||256MB||LAMD LM87800||26nm Toshiba Toggle DDR|
|Crucial m4 256GB||6Gbps||256MB||Marvell 88SS9174||25nm Micron sync MLC|
|Intel 320 Series 300GB||3Gbps||64MB||Intel PC29AS21BA0||25nm Intel MLC|
|Intel 335 Series 240GB||6Gbps||NA||SandForce SF-2281||20nm Intel sync MLC|
|Intel 520 Series 240GB||6Gbps||NA||SandForce SF-2281||25nm Intel sync MLC|
|OCZ Agility 4 256GB||6Gbps||512MB||Indilinx Everest 2||25nm Micron async MLC|
|OCZ Vertex 4 256GB||6Gbps||1GB||Indilinx Everest 2||25nm Intel sync MLC|
|Samsung 830 Series 256GB||6Gbps||256MB||Samsung MCX||27nm Samsung Toggle MLC|
|Samsung 840 Series 250GB||6Gbps||512MB||Samsung MDX||21nm Samsung Toggle TLC|
|WD Caviar Black 1TB||6Gbps||64MB||NA||NA|
We used the following system configuration for testing:
|Processor||Intel Core i5-2500K 3.3GHz|
|Motherboard||Asus P8P67 Deluxe|
|Platform hub||Intel P67 Express|
|Platform drivers||INF update 126.96.36.1990
|Memory size||8GB (2 DIMMs)|
|Memory type||Corsair Vengeance DDR3 SDRAM at 1333MHz|
|Audio||Realtek ALC892 with 2.62 drivers|
|Graphics||Asus EAH6670/DIS/1GD5 1GB with Catalyst 11.7 drivers|
|Hard drives||Corsair Force 3 Series 240GB with 1.3.2 firmware
Corsair Force Series GT 240GB with 1.3.2 firmware
Crucial m4 256GB with 010G firmware
Intel 320 Series 300GB with 4PC10362 firmware
WD Caviar Black 1TB with 05.01D05 firmware
OCZ Agility 4 256GB with 1.5.2 firmware
Samsung 830 Series 256GB with CXM03B1Q firmware
Intel 520 Series 240GB with 400i firmware
OCZ Vertex 4 256GB with 1.5 firmware
Corsair Neutron 240GB with M206 firmware
Corsair Neutron GTX 240GB with M206 firmware
Intel 335 Series 240GB with 335s firmware
Samsung 840 Series 250GB with DXT06B0Q firmware
|Power supply||Corsair Professional Series Gold AX650W|
|OS||Windows 7 Ultimate x64|
Thanks to Asus for providing the systems’ motherboards and graphics cards, Intel for the CPUs, Corsair for the memory and PSUs, Thermaltake for the CPU coolers, and Western Digital for the Caviar Black 1TB system drives.
We used the following versions of our test applications:
- Intel IOMeter 1.1.0 RC1
- HD Tune 4.61
- TR DriveBench 1.0
- TR DriveBench 2.0
- TR FileBench 0.2
- Qt SDK 2010.05
- MiniGW GCC 4.4.0
- Duke Nukem Forever
- Portal 2
Some further notes on our test methods:
- To ensure consistent and repeatable results, the SSDs were secure-erased before almost every component of our test suite. Some of our tests then put the SSDs into a used state before the workload begins, which better exposes each drive’s long-term performance characteristics. In other tests, like DriveBench and FileBench, we induce a used state before testing. In all cases, the SSDs were in the same state before each test, ensuring an even playing field. The performance of mechanical hard drives is much more consistent between factory fresh and used states, so we skipped wiping the HDDs before each test—mechanical drives take forever to secure erase.
- We run all our tests at least three times and report the median of the results. We’ve found IOMeter performance can fall off with SSDs after the first couple of runs, so we use five runs for solid-state drives and throw out the first two.
- Steps have been taken to ensure that Sandy Bridge’s power-saving features don’t taint any of our results. All of the CPU’s low-power states have been disabled, effectively pegging the 2500K at 3.3GHz. Transitioning in and out of different power states can affect the performance of storage benchmarks, especially when dealing with short burst transfers.
The test systems’ Windows desktop was set at 1280×1024 in 32-bit color at a 75Hz screen refresh rate. Most of the tests and methods we employed are publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.
HD Tune — Transfer rates
HD Tune lets us present transfer rates in a couple of different ways. Using the benchmark’s “full test” setting gives us a good look at performance across the entire drive rather than extrapolating based on a handful of sample points. The data created by the full test also gives us fodder for line graphs, which we’ve split up by drive maker. You can click the buttons below each line graph to see how the Samsung 840 Series and our mechanical hard drive compare to different SSDs.
To make the graphs easier to interpret, we’ve greyed out the mechanical drive. The SSD results have been colored by drive maker, as well.
The Samsung 840 Series gets off to a good start, posting the highest sustained read speeds we’ve ever observed in this test. Samsung takes the top two spots, with the 840 Series besting its predecessor by 20MB/s. Impressive.
Well, we knew this was coming. Samsung’s 840 Series is way behind the leaders in HD Tune’s write speed test. The old 830 Series is nearly 150MB/s faster here. That said, the 840 Series does beat a handful of other SSDs, including the popular Crucial m4.
HD Tune runs on unpartitioned drives, a setup that isn’t always ideal for SSDs. For another perspective, we ran CrystalDiskMark’s sequential transfer rate tests, which call for partitioned drives. We used the app’s default settings: a 1GB transfer size with randomized data.
Again, the 840 Series leads in the read speed test but gets dominated when we switch to writes. Samsung’s new hotness manages to stay ahead of a couple of the other SSDs in the write speed test, including the asynchronous SandForce configuration represented by the Corsair Force Series 3. Beating the Intel 320 Series is hardly worth bragging about, though. That drive’s old enough to have a 3Gbps SATA controller.
HD Tune — Random access times
In addition to letting us test transfer rates, HD Tune can measure random access times. We’ve tested with four transfer sizes and presented all the results in a couple of line graphs. We’ve also busted out the 4KB and 1MB transfers sizes into bar graphs that should be easier to read without the presence of the mechanical drive.
TLC memory doesn’t appear to slow down the Samsung 840 Series’ random read performance. The drive has quicker access times than the 830 Series in the 4KB and 1MB tests. The 840 Series is up among the leaders in the 1MB test but not as competitive in the 4KB one.
Surprisingly, the Samsung 840 Series’ random 4KB write performance is pretty decent, just a few microseconds off the quickest access times we’ve measured in that test. However, the 840 Series fades toward the back of the field in the 1MB test. With the larger transfer size, the drive’s write access times are more than a millisecond behind those of the 830 Series.
TR FileBench — Real-world copy speeds
Concocted by resident developer Bruno “morphine” Ferreira, FileBench runs through a series of file copy operations using Windows 7’s xcopy command. Using xcopy produces nearly identical copy speeds to dragging and dropping files using the Windows GUI, so our results should be representative of typical real-world performance. We tested using the following five file sets—note the differences in average file sizes and their compressibility. We evaluated the compressibility of each file set by comparing its size before and after being run through 7-Zip’s “ultra” compression scheme.
|Number of files||Average file size||Total size||Compressibility|
The names of most of the file sets are self-explanatory. The Mozilla set is made up of all the files necessary to compile the browser, while the TR set includes years worth of the images, HTML files, and spreadsheets behind my reviews. Those two sets contain much larger numbers of smaller files than the other three. They’re also the most amenable to compression.
To get a sense of how aggressively each SSD reclaims flash pages tagged by the TRIM command, we run FileBench with the solid-state drives in two states. We first test the SSDs in a fresh state after a secure erase. They’re then subjected to a 30-minute IOMeter workload, generating a tortured used state ahead of another batch of copy tests. We haven’t found a substantial difference in the performance of mechanical drives between these two states. Let’s start with the fresh-state results.
Although the Samsung 830 Series does reasonably well in our first wave of FileBench tests, the 840 Series can’t keep up. The TLC-based drive is slower across the board, often by sizable margins.
Relegated to the bottom half of the pack, the 840 Series trades blows with the Corsair Force Series 3, Crucial m4, and OCZ Agility 4. The Samsung SSD comes out ahead of those drives in most of the tests. Check out the Mozilla and TR results, though. Those file sets are filled with easily compressed data, allowing the Force Series 3 to achieve better performance through write compression.
The Samsung 840 Series’ copy speeds slow down when the drive is put into a simulated used state. There isn’t much change in its position relative to the competition, but performance drops by as much as 19% versus our fresh-state results. The biggest drops come in the Mozilla, MP3, and RAW tests.
Some of the other SSDs experience similar performance drops, so the 840 Series isn’t alone. However, its behavior doesn’t match the more consistent copy speeds of the 830 Series. I suspect the new drive attempts to preserve precious write-erase cycles by taking a more conservative approach to reclaiming trimmed flash pages.
TR DriveBench 1.0 — Disk-intensive multitasking
TR DriveBench allows us to record the individual IO requests associated with a Windows session and then play those results back as fast as possible on different drives. We’ve used this app to create a set of multitasking workloads that combine common desktop tasks with disk-intensive background operations like compiling code, copying files, downloading via BitTorrent, transcoding video, and scanning for viruses. The individual workloads are explained in more detail here.
Below, you’ll find an overall average followed by scores for each of our individual workloads. The overall score is an average of the mean performance score for each multitasking workload.
Neither of the Samsung SSDs fares particularly well in this test, and the 840 Series is the slower of the two. It has a huge lead over the OCZ Agility 4 but still languishes behind the rest of the solid-state field.
The individual test results are somewhat more encouraging, with the Samsung 840 Series climbing up the standings in a couple of instances. However, it’s really slow in the compiling test, which involves writing a lot of small files to the drive.
TR DriveBench 2.0 — More disk-intensive multitasking
As much as we like DriveBench 1.0’s individual workloads, the traces cover only slices of disk activity. Because we fire the recorded I/Os at the disks as fast as possible, solid-state drives also have no downtime during which to engage background garbage collection or other optimization algorithms. DriveBench 2.0 addresses both of those issues with a much larger trace that spans two weeks of typical desktop activity peppered with multitasking loads similar to those in DriveBench 1.0. We’ve also adjusted our testing methods to give solid-state drives enough idle time to tidy up after themselves. More details on DriveBench 2.0 are available on this page of our last major SSD round-up.
Instead of looking at a raw IOps rate, we’re going to switch gears and explore service times—the amount of time it takes drives to complete an I/O request. We’ll start with an overall mean service time before slicing and dicing the results.
The Samsung 840 Series sits near the middle of the field overall, a fair bit behind the lead group of six. Still, the 840 Series is more responsive overall than a number of its peers, including the Crucial m4 and OCZ Agility 4. Care to hazard a guess about what happens when we split service times between reads and writes?
I thought so. With reads, the 840 Series’ mean service time is nearly as quick as that of its predecessor. Writes are a different story entirely. The new model’s write service time is more than twice that of the old 830 Series. Only the Crucial m4 and Intel 320 Series fare worse, and the Intel drive is pretty close.
There are millions of I/O requests in this trace, so we can’t easily graph service times to look at the variance. However, our analysis tools do report the standard deviation, which can give us a sense of how much service times vary from the mean.
Once again, there’s a notable difference between the 840 Series’ competitive position with reads and writes. Only the OCZ Agility 4 and Crucial m4 exhibit more variance in their write service times. With reads, the 840 Series has more consistent results than not only those drives, but also the Corsair Force Series 3, Intel 320 Series, and OCZ Vertex 4.
While we can’t easily graph all the service times recorded by DriveBench 2.0, we can sort them. The graphs below plot the percentage of service times that fall below various thresholds. You can click the buttons below the graphs to see how the Samsung 840 Series compares to SSDs from other drive makers.
The distribution of write service times is surprisingly consistent for all the SSDs, and the Samsung 840 Series gets lost in the crowd. Click through the read results, though. The 840 Series has fewer service times under 0.1 milliseconds than most of the other SSDs, yet it’s ahead of all its peers at the 0.2-ms threshold and beyond. The majority of the drives start to converge around the 0.6-ms threshold. However, the Crucial m4, OCZ Agility 4, and Samsung 830 series don’t catch up until we approach the one-millisecond threshold.
As the distribution plots illustrate, service times over 100 milliseconds make up a tiny fraction of the overall results. Those extremely long service times have the potential to cause the sort of hitching that a user might notice, so we’ve graphed the individual percentages for each drive.
No problems here. The Samsung 840 Series doesn’t have the lowest percentages of extremely long service times, but it comes pretty close with both reads and writes.
Don’t let the tiny fractions throw you. Our DriveBench 2.0 trace covers over 10 million I/O requests spread over two weeks of activity. Even a small percentage represents a sizable number of sluggish service times.
Our IOMeter workloads feature a ramping number of concurrent I/O requests. Most desktop systems will only have a few requests in flight at any given time (87% of DriveBench 2.0 requests have a queue depth of four or less). We’ve extended our scaling up to 32 concurrent requests to reach the depth of the Native Command Queuing pipeline associated with the Serial ATA specification. Ramping up the number of requests also gives us a sense of how the drives might perform in more demanding enterprise environments.
We run our IOMeter tests using the fully randomized data pattern, which presents a particular challenge for SandForce’s write compression scheme. We’d rather measure SSD performance in this worst-case scenario than using easily compressible data.
Adding the Samsung 840 Series to our catch-all IOMeter graphs made them too difficult to read, so we’ve split the results by drive maker. You can compare the 840 Series’ performance to that of the competition by clicking the buttons below each graph.
The web server test is made up exclusively of read requests, so we’ll deal with it separately. Here, the Samsung 840 Series fares exceptionally well, beating its forebear and everything else we’ve tested. Unlike some of the other SSDs, the 840 Series’ transaction rate doesn’t fall off appreciably as the number of concurrent I/O requests scales beyond eight.
All of the other IOMeter tests mix read and write requests, and the 840 Series suffers as a result. It’s slower than the 830 Series almost across the board and only comes out ahead of the SandForce-based SSDs at higher queue depths. That said, the 840 Series sticks pretty close to the Corsair Force Series 3 at lower queue depths and beats the Crucial m4, Intel 320 Series, and OCZ Agility 4 handily overall.
Before timing a couple of real-world applications, we first have to load the OS. We can measure how long that takes by checking the Windows 7 boot duration using the operating system’s performance-monitoring tools. This is actually the first test in which we’re booting Windows 7 off each drive; up until this point, our testing has been hosted by an OS housed on a separate system drive.
Level load times
Modern games lack built-in timing tests to measure level loads, so we busted out a stopwatch with a couple of reasonably recent titles.
There’s only about a one-second difference between most of the SSDs in our load time tests. The Samsung 840 Series is never more than a couple of milliseconds out of first place and even takes the lead in Portal 2, albeit by a hair. As we’ve seen throughout our results, the lone mechanical hard drive doesn’t even come close to matching the performance of the SSDs.
We tested power consumption under load with IOMeter’s workstation access pattern chewing through 32 concurrent I/O requests. Idle power consumption was probed one minute after processing Windows 7’s idle tasks on an empty desktop.
The Samsung 840 Series’ idle power consumption is lower than any other SSD we’ve tested. In fact, the drive draws less than a third of the power required by the 830 Series in this state.
Our IOMeter load is considerably more demanding, as the higher power consumption numbers attest. Here, the Crucial m4 and Intel 320 Series jump to the top of the standings. The Samsung 840 Series still draws about 2W less than its predecessor, though, and its power consumption is comparable to the collection of SandForce-based SSDs in the 2.8-3.1W range.
The value perspective
Welcome to another one of our famous value analyses, which adds capacity and pricing to the performance data we’ve explored over the preceding pages. We used Newegg prices to even the playing field, and we didn’t take mail-in rebates into account when performing our calculations.
First, we’ll look at the all-important cost per gigabyte, which we’ve obtained using the amount of storage capacity accessible to users in Windows.
Unlike Intel’s recently introduced 335 Series, which is selling for much more than the suggested retail price, the Samsung 840 Series costs a little bit less than the MSRP. $180 for 250GB translates to a lower cost per gigabyte than any of the other SSDs. Samsung’s own 830 Series comes the closest, but it’s being phased out and won’t be in stock for much longer.
Our remaining value calculation uses a single performance score that we’ve derived by comparing how each drive stacks up against a common baseline provided by the Momentus 5400.4, a 2.5″ notebook drive with a painfully slow 5,400-RPM spindle speed. This index uses a subset of our performance data described on this page of our last SSD round-up.
Well, this isn’t surprising. The Samsung 840 Series’ comparatively weak write performance keeps it out of the top tier in our overall performance metric. Still, the drive scores higher than a handful of SSDs that includes the Corsair Force Series 3, Crucial m4, Intel 320 Series, and OCZ Agility 4.
Now for the real magic. We can plot this overall score on one axis and each drive’s cost per gigabyte on the other to create a scatter plot of performance per dollar per gigabyte. The best place on the plot is the upper-left corner, which combines high performance with a low price.
The scatter plot nicely puts things into perspective. There are lots of drives that offer better performance than the Samsung 840 Series, but they all cost more. In fact, with the exception of the 830 Series, those faster drives cost a fair bit more.
If we consider the 840 Series versus its more direct competition, the drive looks like a pretty sweet deal. It’s cheaper than drives in the second tier but scores higher on our performance scale.
Those expecting the Samsung 840 Series to be a true successor to the 830 Series will no doubt be disappointed. The new drive is slower than its predecessor overall and quite sluggish with both sequential and random writes. Samsung’s use of TLC memory is almost certainly to blame for the slower write performance, but the firm hasn’t bet the farm on triple-stuffed NAND. The 840 Pro is the true follow-up to the 830 Series, and it features MLC chips with two bits per cell. Of course, the Pro also costs 50% more than the 840 Series. Clearly, it’s a different class of drive.
The 840 Series is really a budget SSD. When you look at its performance versus other offerings in that arena—the Crucial m4, OCZ Agility 4, and asynchronous SandForce drives like the Corsair Force Series 3—the 840 Series is very competitive. Even its plodding write speeds don’t seem so bad when compared with those direct rivals. Factor in the drive’s low idle power consumption and slick utility software, and it starts to look pretty desirable. And don’t forget that the 840 Series costs less than all of its peers.
Of course, we still have questions surrounding the 840 Series’ endurance; the useful life of the drive is kind of a big deal. Endurance is particularly important considering the 840 Series’ NAND, whose finer geometry and extra bit per cell both conspire to shorten the life of the flash. Given those obvious red flags, we wish Samsung were more forthcoming about the 840 Series’ expected lifespan.
Samsung’s ability to sort the NAND it produces selectively certainly leaves room for optimism. The fact that the company has been dealing with the stringent validation requirements of big-name PC makers for years lends some credibility to the final product, too. So does the three-year warranty, even if it doesn’t tell us how much data can be written to the drive during that time.
As long as its NAND holds up, the 840 Series looks like a good option for anyone seeking an inexpensive path to solid-state storage. The slim case and low idle power consumption are especially appealing for notebooks, which may be the perfect environment for this drive. Thing is, the shadow of the 830 Series looms large even as its supply fades. The 256GB model costs 10 bucks more than the equivalent 840 Series but offers a little more storage and a lot more performance.
The 830 Series is still the best option for desktop use… while it lasts. Notebook users more concerned with NAND endurance than battery life are probably better off taking that route, too, but road warriors should give the 840 Series a closer look. Its combination of low power consumption and a low cost per gigabyte is a potent cocktail for mobile systems.