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Samsung 840 EVO SSD: Tested At 120, 250, 500, And 1000 GB
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1. The Evolution Of Samsung As An SSD Giant

Imagine the following conversation between two Samsung executives:

"What are we going to do tonight?”. Suit number two replies, “The same thing we do every night. Try and take over the world.”

Samsung's previous-gen 470 and 830 SSDsSamsung's previous-gen 470 and 830 SSDs

"Yeah, okay. How?"

"Branded memory products."

"Memory products? I'm sold. Let's do it."

And so that's what the company is doing. In an era where everything needs DRAM and NAND flash, the fabricator is king. If you’re the largest fabricator...well, you're halfway there. This is a target-rich environment, too. With SSD shipments still accelerating, it seems like any company could stay solvent selling solid-state storage. But that's just not the case. This market is dominated by the companies producing the NAND, and Samsung's biggest. 

Working its way to the top of the SSD space didn't happen overnight, though. It took successive products offering strong performance, enough time to reassure folks that the drives are reliable, and ginormous quantities of flash.

Samsung's first drives were a lot like other early SSDs. I call them proto-SSDs; they're the missing link between old-school flash-based storage and more modern architectures, which we were introduced to roughly around the time Intel launched its X25-M and -E. Before then, SSDs were sequential transfer machines, lacking a focus on the small-block random access agility we take for granted today. Some lacked native command queuing, the TRIM command was still a twinkle on the horizon, and many models employed the IDE interface with a SATA bridge. Samsung didn't join the new-school SSD business until 2010, despite its presence from the beginning, selling Jurassic-period drives to OEMs.

Once the company really started swinging its scepter at the desktop SSD market, its ascension was swift. The 470 was really Samsung's first foray into the über-competitive consumer space. It was fine in its own right, but was overshadowed by the flood of SandForce-based models (not to mention Intel's efforts). Then there was the 830, which did well among press and end users alike. Versions of the 830 became some of the first 6 Gb/s SSDs shipping in laptops, most notably those from Apple. Deserving praise was doled out liberally. Samsung had the ability to develop everything in-house, and the 830 showed off the significance of that advantage even more than the 470.

A year later, the company split its consumer offerings into two separate families: the 840 Pro and 840. They're similar in many ways, except the flagship 840 Pro sports Toggle-mode DDR flash. It's a great product, one of the fastest we've tested, and enthusiasts love it. But in the grand scheme of things, it's not as important as the 840, built from three-bit-per-cell NAND. Several companies claimed that drives with this memory technology were imminent well before the 840's launch. However, Samsung was the first to get it done. That wasn't the drive we were looking for, though. Absurdly low endurance ratings? Crazy high latency? No thanks. In fact, we weren't sure why the 840 made sense at the time. Back then, capacities were increasing and prices were dropping fast on the familiar MLC-based SSDs.

Samsung's new 840 EVOSamsung's new 840 EVO

Getting that first TLC-based drive out there wasn't about selling drives at retail. Rather, it was about locking down the OEM sales that drive the SSD industry. Those OEMs sell a lot of volume and are super price-sensitive. Cutting a few bucks from a drive doesn't mean a ton to you or me, but dropping the bill of materials on a popular notebook is huge for a company like Apple or Dell.

And as it turned out, the 840 wasn’t a hopeless dog, either. It didn't die after 1000 P/E cycles, and it wasn't particularly slow. In fact, we have a drive that went a full 3207 P/E cycles before it cratered last December. I've seen similar results from others, so the endurance debate may be a red herring in consumer workloads. Write performance was modest, and read speeds exceeded most two-bit-per-cell competitors.

Overall, Samsung says the drive was about increasing adoption rates, and the company's plan seems to have worked. Representatives claim Samsung served up 2,524,699 840s already, good for an astounding 20% of the aftermarket. That means one out of every five SSDs sold through e-tailers since the launch was an 840. If that stat is true, it's amazing. How do you top such a thing?

Samsung's Next-Gen 840: The EVO

We're not sure if EVO stands for evolution or nothing specific at all. Regardless, the drive's inner workings, hidden under a new metal chassis, are definitely an improvement on the original 840 and not a ground-up redesign. To be fair, the 840 wasn't broken, so no fix was necessary. But with a tuned controller, 19 nm NAND, and a technology that Samsung calls Turbo Write, the end result is...different.

Five 840 EVO models are launching early August in most major markets. Switching from 21 nm, 64 Gb die to 19 nm, 128 Gb die allows the EVO to double in capacity. The old 840 topped out at 500 GB; the EVO maxes out at 1 TB. That gives us a line-up with 120, 250, 500, 750, and 1000 GB options. More capacity is always a good thing, particularly since Crucial's 960 GB M500 suffered poor availability after it launched. The 750 GB model is a little unusual, but we're down with that, too.

Samsung 840 EVO
120 GB
250 GB
500 GB
750 GB
1 TB
MSRP
$110
$190
$370
$530
$650
Controller
400 MHz Samsung MEX, three-core ARM Cortex-R4
NAND
19 nm Samsung Toggle-mode NAND (400 Mb/s), three-bit-per-cell
Form Factor/Interface
2.5", 7 mm Z-height, SATA 6Gb/s
Warranty
Three Years
Seq. Read/Write (MB/s)
540 / 410
540 / 520
Rand. 4 KB Read QD 32 (IOPS)
94,000
97,000
98,000
98,00098,000
Rand. 4 KB Write QD 32 (IOPS)
35,000
66,000
90,000
90,00090,000
Rand. 4 KB Read QD 1 (IOPS)
10,000
10,00010,00010,00010,000
Rand. 4 KB Write QD 1 (IOPS)
33,000
33,00033,00033,00033,000
Die Count
8
16
32
48
64

That's five EVO models, stretching from 120 GB to 1 TB. And they're shipping at the 840's price points, too. Samsung is really proud of this, though we'd frankly like to see three-bit-per-cell NAND on a smaller process pulling prices down instead of propping them up. In time, perhaps. Likely, the company is hoping that more performance and capabilities are what you'll focus on.

A new version of Samsung's management software, SSD Magician, will also roll out alongside the EVO, sweetening the deal with revamped cloning functionality and a feature called RAPID, which is host-side DRAM caching that works with Windows to push storage performance beyond the limitations of a 6 Gb/s SATA interface.

Speaking of speed-ups, check out those specs. If you're familiar with the original 840, then you see that the write performance is radically improved. How does Samsung achieve this? We'll dig deeper on the next page.

2. The 840 EVO's Bag Of New Tricks

The Flash

There are a number of minor changes that turn the mild-mannered, economical 840 into a sometimes-fire-breathing beast. It all starts with the flash.

Previously, Samsung didn't really want to talk about the 840's memory, though it appears the company was using 64 Gb NAND dice manufactured at 21 nm. A 64 Gb die holds 8 GB of data; the new 128 Gb density stores 16 GB per die. So, fewer dice accommodate the same amount of information.

This is enabled by the reduction in feature size, as more transistors fit into a given unit of physical space. Every time manufacturing steps forward, companies like Samsung get more dice from each wafer. When you consider the evolution from one to two to three bits of data per memory cell, it's no wonder we're seeing big, affordable 1 TB SSDs.

The problem is that smaller geometry increases latency and has an adverse effect on write endurance. That third bit per cell complicates matters too, having some effect on read latency and a more substantial impact on writes. This is why the vanilla 840 offers great read performance and mediocre write speeds compared to much of the competition.

Not only does Samsung have to engineer its way around the flash's inherent shortcomings, but also face the extra complexity of NAND management and error correction. The company typically doesn't give away much information about how it extends endurance to livable levels. In the case of its 840 EVO, however, it went into a bit more depth.

Turbo Write

SanDisk was the first company to use MLC NAND as emulated SLC for very fast programming. Toshiba is doing something similar with its two-bit-per-cell MLC. However, Samsung arguably gets the most mileage from this technique because it's using TLC NAND. Though each technology works a little differently, the idea is that, by setting aside some amount of memory to operate in SLC mode, performance improves substantially. As an added bonus, there are scenarios where this sort of caching can improve a drive's overall endurance. Samsung's approach does confer rigteous write numbers, even if that's only until the cache fills up.

The implementation involves a fixed array of NAND cells on a per-device basis. Take a chunk of triple-level-cell memory, use it as SLC, and you lose 66% of its capacity. For instance, the 1 TB 840 EVO has 36 GB carved out for Turbo Write, giving you 12 GB of emulated SLC. That's actually quite a bit of cache, though a little bit goes a long way. Here's the breakdown by capacity:

840 EVO Turbo Write
120 GB
250 GB
500 GB
750 GB
1 TB
Sacrificed TLC Capacity
9 GB
9 GB
18 GB
27 GB
36 GB
Turbo Write SLC Cache
3 GB
3 GB
6 GB
9 GB
12 GB

Once the drive's cache is full, spillover goes directly to the three-bit-per-cell NAND. If you try to write at the drive's top speed for longer than it takes to fill the cache, performance drops back to the 840's original peaks.

In the chart above, I'm writing sequentially in Iometer. Depending how long the write lasts, you can see how much the throughput varies. At the end of 10 seconds, the 120 GB model is pushing 331 MB/s. Spend 20 seconds writing 128 KB blocks and the cache overrun is even greater.

Based on the table above my chart, the 120 GB 840 EVO has about 3 GB of usable cache. That means it only takes about nine seconds to fill at 330 MB/s. Samsung says it'll do more than 400 MB/s with Turbo Write, though. Obviously, as the cache fills up, speed is dropping precipitously. In this case, it dips as low as 169 MB/s at the end of one minute. This works so well in the real world because you're probably not going to be writing for that long. Desktop usage patterns really lend themselves to this type of acceleration.

Thermal Protection

Tying it all together (the enhanced write speed, a new controller, and updated flash) is thermal protection. Though not particularly sexy, in space-constrained enclosures, SSDs can get scorching hot. This is an issue for the components inside, particularly triple-level cell NAND, most of which shouldn't be operated in excess of 70 degrees Celsius. Too much heat can shift the voltage thresholds for a memory cell out of bounds, creating chaos.

To solve that problem, most newer drives employ some form of thermal throttling. Just like a CPU when it gets too toasty, a properly protected SSD will ease off of writes until the temperatures fall below a trigger threshold. In the EVO's case, that's 70 degrees. Reading from the flash doesn't require much voltage, but programming and erasing do. Fortunately, Samsung has a reputation for relatively low power consumption most of the time, though TLC NAND inherently draws more.

3. Inside Samsung's 840 EVO

Getting into the svelte gunmetal-grey chassis is a snap, so long as you have a #5 pentalobe screwdriver handy. You'll find two screws under the label and one that's plainly visible. Don't even bother removing the label; just push the bit right through it.

There are no thermal pads, stickers, or adhesives under the cover. The drive's top, circuit board, and bottom separate as easily as oil and water.

500 GB 840 EVO circuit board500 GB 840 EVO circuit board

This is the 500 GB model's PCB. Samsung's 120 GB drive is actually shorter, as you can see in the side-by-side shot below. Each NAND package plays host to eight dice, except on the 120 GB drive, which uses two quad-die packages. Otherwise, each package's octet of 128 Gb Toggle-mode NAND delivers 128 GB capacity.

500 GB (left) and 120 GB (right) 840 EVO circuit boards500 GB (left) and 120 GB (right) 840 EVO circuit boards

The MEX 400 MHz triple-core Cortex-R4-based controller is labeled S4LN045X01-B030. This new revision runs 100 MHz faster than the older 840's processor, and will also be able to apply Opal 2.0-compatible encryption, either through the drive itself or through Windows 8's BitLocker Drive Encryption, once an upcoming firmware update is certified. This is big news in the self-encrypting drive space, since there aren't many desktop drives with Opal 2.0 support yet. Naturally, this will change as competing vendors refresh their product lines.

500 GB 840 EVO, from the back500 GB 840 EVO, from the back

Lastly, we see the drive's LPDDR2 DRAM cache. In the picture of the 500 GB 840 EVO, it's a 512 MB package. Samsung is deploying 1 MB of cache for every gigabyte of capacity, which is fairly standard these days.

4. Test Setup And Benchmarks

Our consumer storage test bench is based on Intel's Z77 Platform Controller Hub paired with an Intel Core i5-2400 CPU. Intel's 6- and 7-series chipsets are virtually identical from a storage perspective. We're standardizing on older RST 10.6.1002 drivers for the foreseeable future.

Changes in RST's driver packages occasionally result in subtle performance changes. They can also lead to some truly profound variance in scores and results as well, depending on the driver revision. Some versions flush writes more or less frequently. Others work better in RAID environments. In fact, builds 11.2 and newer even support the TRIM command in RAID. Regardless, results obtained with one revision may or may not be comparable to results obtained with another, so sticking with one build across all tests is mandatory.

Test Hardware
ProcessorIntel Core i5-2400 (Sandy Bridge), 32 nm, 3.1 GHz, LGA 1155, 6 MB Shared L3, Turbo Boost Enabled
MotherboardGigabyte G1.Sniper M3
MemoryG.Skill Ripjaws 8 GB (2 x 4 GB) DDR3-1866 @ DDR3-1333, 1.5 V
System Drive Kingston HyperX 3K 240 GB, Firmware 5.02
Tested DrivesSamsung 840 EVO 120 GB SATA 6Gb/s, Firmware: EXT0AB0Q

Samsung 840 EVO 250 GB SATA 6Gb/s, Firmware: EXT0AB0Q

Samsung 840 EVO 500 GB SATA 6Gb/s, Firmware: EXT0AB0Q

Samsung 840 EVO 1 TB SATA 6Gb/s, Firmware: EXT0AB0Q

SanDisk Ultra Plus 64 GB SATA 6Gb/s, Firmware: X211200

SanDisk Ultra Plus 128 GB SATA 6Gb/s, Firmware X211200

SanDisk Ultra Plus 256 GB SATA 6Gb/s, Firmware X211200

Samsung 840 Pro 256 GB SATA 6Gb/s, Firmware DXM04B0Q

Samsung 840 Pro 128 GB SATA 6Gb/s, Firmware DXM04B0Q

Samsung 840 250 GB SATA 6Gb/s, Firmware DXT08B0Q

Samsung 840 120 GB SATA 6Gb/s, Firmware DXT08B0Q

SanDisk Extreme II 120 GB, Firmware: R1311

SanDisk Extreme II 240 GB, Firmware: R1311

SanDisk Extreme II 480 GB, Firmware: R1311

Seagate 600 SSD 240 GB SATA 6Gb/s, Firmware: B660

Intel SSD 525 30 GB mSATA 6Gb/s, Firmware LLKi

Intel SSD 525 60 GB mSATA 6Gb/s, Firmware LLKi

Intel SSD 525 120 GB mSATA 6Gb/s, Firmware LLKi

Intel SSD 525 180 GB mSATA 6Gb/s, Firmware LLKi

Intel SSD 525 240 GB mSATA 6Gb/s, Firmware LLKi

Intel SSD 335 240 GB SATA 6Gb/s, Firmware: 335s

Intel SSD 510 250 GB SATA 6Gb/s, Firmware: PWG2

OCZ Vertex 3.20 240 GB SATA 6Gb/s, Firmware: 2.25

OCZ Vector 256 GB SATA 6Gb/s, Firmware: 2.0

Samsung 830 512 GB SATA 6Gb/s, Firmware: CXMO3B1Q

Crucial m4 256 GB SATA 6Gb/s Firmware: 000F

Plextor M5 Pro 256 GB SATA 6Gb/s Firmware: 1.02

 Corsair Neutron GTX 240 GB SATA 6Gb/s, Firmware: M206
Graphics
MSI Cyclone GTX 460 1 GB
Power Supply
Seasonic X-650, 650 W 80 PLUS Gold
Chassis
Lian Li Pitstop
RAID
LSI 9266-8i PCIe x8, FastPath and CacheCade AFK
System Software and Drivers
Operating
System
Windows 7 x64 Ultimate
DirectX
DirectX 11
Drivers
Graphics: Nvidia 314.07
RST: 10.6.1002
IMEI: 7.1.21.1124
Benchmarks
Tom's Hardware Storage
Bench v1.0
Trace-Based 
IOmeter 1.1.0# Workers = 1, 4 KB Random: LBA=16 GB, varying QDs, 128 KB Sequential, 8 GB LBA Precondition, Exponential QD Scaling
PCMark 8
Storage Benchmark
PCMark 7
Secondary Storage Suite
PCM Vantage
Storage Suite
FIO
2.0.14
5. Results: 128 KB Sequential Reads

Fantastic sequential read and write performance is a trademark of modern SSDs. To measure it, we use incompressible data over a 16 GB LBA space, then test at queue depths from one to 16. We're reporting these numbers in binary (where 1 KB equals 1024) instead of decimal numbers (where 1 KB is 1000 bytes). When necessary, we're also limiting the scale of the chart to enhance readability.

128 KB Sequential Read

The y-axis starts at 300 MB/s because we need all of the separation we can get to distinguish the larger three 840 EVO drives. Samsung's 120 GB model has a funkier trajectory, starting under 400 MB/s, peaking at a queue depth of two, above the higher-capacity models, and then stumbling again at a queue depth of 16. Such is life for a drive with just eight dice to call its own.

Folding in the rest of the field, only Intel's SSD 335 working with incompressible data at low queue depths stands out. 

With a single outstanding command, 100 MB/s separates the fastest and slowest SSDs. Samsung's 840 EVOs are in the thick of it.

Are you wondering which of the drives we tested fares best in our 128 KB sequential read test? Here's a break-down of the maximum observed read performance during Iometer-based benchmarking.

All four 840 EVO drives set up shop in the middle of the pack, though almost every sample lands roughly in the same ballpark. They all push past 500 MB/s at least.

6. Results: 128 KB Sequential Writes

128 KB Sequential Write

This is where the analysis gets more complicated. When we tested SanDisk's Extreme II, our Iometer-based setup yielded specific, detrimental results. They weren't terrible, but we did notice that a larger-than-typical LBA range upset the drives. We suspect their behavior was attributable to SanDisk's nCache technology.

In the same way, the length of the testing at each queue depth means our results are stacked against the 840 EVO's maximum speed, penalizing the larger models due to their comparatively larger Turbo Write caches.

Take the 120 GB 840 EVO as an example. It should be hitting ~400 MB/s. But as I explained, it sets aside 9 GB of capacity to cache 3 GB of writes. Overflow is written to the remaining three-bit-per-cell memory at a slower rate. Samsung's 250 GB 840 EVO starts almost 100 MB/s faster. If we stopped this test after just a couple of seconds, though, you'd see throughput closer to 500 MB/s since the cache wouldn't be full yet.

The 500 GB and 1 TB versions can't quite hit the 500+ MB/s we'd expect because, again, we're exceeding the capacity of their respective caches. But more space set aside and additional parallelism facilitate results that come closer to Samsung's maximum specified Turbo numbers.

Somewhat unsurprisingly, the 120 GB 840 EVO butts up against the 250 GB 840. Samsung's older drive doesn't enjoy the faster controller frequency or on-drive caching. Those features help the 120 GB 840 EVO almost keep up with a vanilla 840 almost twice its size.

The 250 GB 840 EVO matches Intel's SSD 335 working on non-compressible data, and the two larger 840 EVOs nearly claim top positions through our test.

Samsung's Turbo Write technology propels the 120 GB 840 EVO into a spot between the 250 and 120 GB 840s. The 250 GB 840 EVO is sandwiched between a pair of Intel drives.

The 840 EVOs don't achieve their maximum numbers in our Iometer test, but 460 MB/s certainly isn't an outcome we'd dismiss. 

7. Results: 4 KB Random Reads

Technically, "random" translates to a consecutive access that occurs more than one sector away. On a mechanical hard disk, this can lead to significant latencies that hammer performance. Spinning media simply handles sequential accesses much better than random ones, since the heads don't have to be physically repositioned. With SSDs, the random/sequential access distinction is much less relevant. Data are put wherever the controller wants, so the idea that the operating system sees one piece of information next to another is mostly just an illusion.

4 KB Random Reads

Turbo Write obviously doesn't help with random reads, so the complicated situation from the previous page doesn't apply. Each drive lands where we'd expect. They all hit the 90,000 IOPS mark at a queue depth of 32 and achieve 10,000 IOPS at a queue depth of one.

Samsung specifically mentioned that it optimized performance for a single outstanding command, and those efforts show. The fact that Samsung is seeing these read speeds and using triple-level-cell NAND is going to make a few competitors green with envy.

Samsung's newest efforts are eclipsed by a small cadre of performance-oriented SSDs, but by slim and frankly inconsequential margins. The 840 EVOs are faster than the 512 GB 830 and both 840s.

We look to maximum 4 KB read speeds for additional perspective. Some separation does occur, but again it's not particularly significant. It doesn't take much flash to achieve spectacular read performance, so we'll need to move on to writes for a clearer picture of performance differentiation.

8. Results: 4 KB Random Writes

4 KB Random Write

The performance hit finally becomes apparent when we start ripping off 4 KB random writes. Samsung's 120 GB 840 EVO trails the rest of the crew, but then again it's only expected to hit 35,000 IOPS with a boost from Turbo Write. The 250 GB model plateaus with four outstanding commands. It does hit Samsung's specified target though, settling around 66,000 IOPS. Neither the 500 GB nor the 1 TB versions quite make it to 90,000 IOPS, though the largest configuration nearly gets there at a queue depth of eight.

Without question, random write performance is extremely important. Early SSDs didn't do well in this discipline, seizing up even in lightweight workloads. Newer drives proffer more than 100x the performance of solid-state storage from 2007. However, we also see a point of diminishing returns on the desktop.

It'd be easy to single out the 120 GB 840 EVO as the family's misfit. Just remember that it's only slow by comparison. In absolute terms, it still blows away the responsiveness of a mechanical disk.

9. Results: Tom's Hardware Storage Bench v1.0

Storage Bench v1.0 (Background Info)

Our Storage Bench incorporates all of the I/O from a trace recorded over two weeks. The process of replaying this sequence to capture performance gives us a bunch of numbers that aren't really intuitive at first glance. Most idle time gets expunged, leaving only the duration that each benchmarked drive was actually busy working on host commands. So, by taking the ratio of that busy time and the the amount of data exchanged during the trace, we arrive at an average data rate (in MB/s) metric we can use to compare drives.

It's not quite a perfect system. The original trace captures the TRIM command in transit, but since the trace is played on a drive without a file system, TRIM wouldn't work even if it were sent during the trace replay (which, sadly, it isn't). Still, trace testing is a great way to capture periods of actual storage activity, a great companion to synthetic testing like Iometer.

Incompressible Data and Storage Bench v1.0

Also worth noting is the fact that our trace testing pushes incompressible data through the system's buffers to the drive getting benchmarked. So, when the trace replay plays back write activity, it's writing largely incompressible data. If we run our storage bench on a SandForce-based SSD, we can monitor the SMART attributes for a bit more insight.

Mushkin Chronos Deluxe 120 GB
SMART Attributes
RAW Value Increase
#242 Host Reads (in GB)
84 GB
#241 Host Writes (in GB)
142 GB
#233 Compressed NAND Writes (in GB)
149 GB

Host reads are greatly outstripped by host writes to be sure. That's all baked into the trace. But with SandForce's inline deduplication/compression, you'd expect that the amount of information written to flash would be less than the host writes (unless the data is mostly incompressible, of course). For every 1 GB the host asked to be written, Mushkin's drive is forced to write 1.05 GB.

If our trace replay was just writing easy-to-compress zeros out of the buffer, we'd see writes to NAND as a fraction of host writes. This puts the tested drives on a more equal footing, regardless of the controller's ability to compress data on the fly.

Average Data Rate

The Storage Bench trace generates more than 140 GB worth of writes during testing. Obviously, this tends to penalize drives smaller than 180 GB and reward those with more than 256 GB of capacity.

The 840 EVOs crush our average data rate chart, representing read and write performance combined. Despite the perception that this is a value-oriented product, we've already shown the 840 EVO's read speeds to be as good as any other SSD, while Samsung's Turbo Write feature augments write performance. The 1 TB and 500 GB 840 EVOs take second and fourth place, while the other two capacities turn in respectable performance as well.

10. Results: Tom's Hardware Storage Bench, Continued

Service Times and Standard Deviation

Beyond the average data rate reported on the previous page, there's even more information we can collect from Tom's Storage Bench. For instance, mean (average) service times show what responsiveness is like on an average I/O during the trace.

It would be difficult to graph the 10 million I/Os that make up our test, so looking at the average time to service an I/O makes more sense. We can plot mean service times for reads against writes. That way, drives with better latency show up closer to the origin; lower numbers are better.

You really want to see your SSD serving up I/Os like a ninja tossing throwing stars (not altogether a bad analogy for I/O latency). He might be able to wing a number of them each second, but they all take time to reach their destination. If the host asks for a piece of data, how long does it take for the storage subsystem to respond with the right information? Splitting up read and write service times helps us understand each drive's strengths and weaknesses.

The 120 GB Samsung 840 EVO plots so far off the scale for writes that it's outside of our visible range.

All of the drives we're testing today demonstrate great mean read service times. Given their triple-level cell NAND, however, we have to give credit to Samsung's 840 EVOs for keeping up with the MLC-based competition.

The 840 Pro finishes just ahead of OCZ's Vector, and the 1 TB 840 EVO is just one microsecond behind. The 250 and 500 GB models fall in right after that, mixed in with the smaller 840 Pro, Intel's SSD 335, and the Vertex 450. Samsung's 120 GB 840 EVO is further back, though still in front of the 256 GB m4 and Neutron GTX.

This trace has over twice as many read IOs as writes. But writes account for more throughput. And even thought the three-bit-per-cell flash should be slower, Toggle-mode NAND and a faster controller could be keeping the 840 EVO competitive.

The 120 GB 840 EVO stands out for its high latency. On average, Samsung's entry-level model took 2.14 ms to sevice a request, which is three times longer than the first-place Vector.

In fact, two Indilinx-powered drives from OCZ take first and second place, while SanDisk's Extreme II snatches the bronze. The largest 840 EVOs land right in the middle, which isn't bad given Samsung's architecture and the write-heavy nature of our trace. Although the 840 EVOs don't lead the field, if nothing else, we're pleased to see triple-level cell NAND keeping up with the MLC competition.

11. Results: PCMark 7 And PCMark Vantage

Futuremark's PCMark 7: Secondary Storage Suite

PCMark 7 uses the same trace-based technology as our Storage Bench v1.0 for its storage suite testing. It employs a geometric mean scoring system to generate a composite, so we end up with PCMarks instead of a megabytes per second. One-thousand points separate the top and bottom, but that encompasses a far larger difference than the score alone indicates.

PCMark 7 is a vast improvement over the older PCMark Vantage, at least for SSD benchmarking. The storage suite is comprised of several small traces. At the end, the geometric mean of those scores is scaled with a number representing the test system's speed. The scores generated are much different from PCMark Vantage, and many manufacturers are predisposed to dislike it for that reason. It's hard to figure out how PCMark 7 "works" because it uses a sliding scale to generate scores. Still, it represents one of the best canned benchmarks for storage, and if nothing else, it helps reinforce the idea that the differences in modern SSD performance don't necessarily amount to a better user experience in average consumer workloads.

Samsung's high-performance flagships plant a flag at the top. From there, we see three different 840 EVO drives. Given what we know about the new drive's read performance and the fact that PCMark 7 is probably a prototypical workload that benefits from Turbo Write, maybe we shouldn't be so surprised.

PCMark 7 is great because it reflects real-world SSD performance differentials. Some dislike the fact that the composite scores are so similar from drive to drive, but it helps illustrate the real world feel among drives, and that means a fast drive and a slow drive aren't as far apart as the other benches might indicate.

Futuremark's PCMark Vantage: Hard Drive Suite

PCMark's Vantage isn't the paragon of SSD testing, mainly just because it's old and wasn't designed for the massive performance solid-state technology enables. Intended to exploit the new features in Windows Vista, Vantage was certainly at the forefront of consumer storage benching at the time. Vantage works by taking the geometric mean of composite storage scores and then scaling them a lot like PCMark 7 does. But in Vantage's case, this scaling is achieved by arbitrarily multiplying the geometric sub-score mean by 214.65. That scaling factor is supposed to represent an average test system of the day (a system that's now close to a decade behind the times). PCMark 7 improves on this by creating a unique system-dependent scaling factor and newer trace technology. Why bother including this metric, then? A lot of folks prefer Vantage in spite of or because of the cartoonish scores and widespread adoption. That, and the fact that most every manufacturer uses the aged benchmark in box specs and reviewer-specific guidelines.

12. Results: Robocopy File Copy Performance

File Copy Performance with Microsoft Robocopy

Microsoft's Robocopy, a CLI directory replication command, gradually replaced the older xcopy. It rocks a whole host of features that make it the logical choice for transferring a large number of files. It's multi-threaded, has a ton of options, and generally outperforms vanilla Windows copy operations. Best of all, it's built right in to Redmond's operating system. Especially useful for network copy operations and backups, Robocopy doesn't stop to ask you one hundred questions while it copies over your music collection, either.

The reality of benchmarking file copy performance is that you need something fast to copy from and something fast to copy to. This is most important with SSDs. It doesn't matter if your drive can write sequentially at 500 MB/s if the source files are hosted on a USB 2.0-attached external hard drive. We're copying our test files from an Intel SSD DC S3700 to the drives in the chart below, taking source speed out of the equation.

There are 9065 files comprising the 16.2 GB payload. Some of the files are huge (up to 2 GB), while others are best described as tiny. On average, that's around 1.8 MB per file. The files are a mix of music, program, pictures, and random file types.

It's fair to say that this chart would look much different if we were copying from a hard drive to a SSD. Even if the disk drive's sequential throughput wasn't a bottleneck, it'd still choke on the smaller files.

Samsung's 840 EVOs don't quite show up where we were expecting. The 500 GB model comes close to the 128 GB 840 Pro, while the 1 TB model squares up against SanDisk's 120 GB Extreme II. You'd think that write caching via Turbo Write would excel, especially the biggest model and its 12 GB of simulated SLC memory. For comparison, the 120 GB model is just slightly faster than the 64 GB Ultra Plus from SanDisk. Meanwhile, the 250 GB drive is just three seconds ahead of the 128 GB Ultra Plus.

13. Results: Power Consumption

Idle Power Consumption

Idle consumption is the most important power metric for consumer and client SSDs. After all, solid-state drives complete host commands quickly, and then drop back down to idle. Aside from the occasional background garbage collection and house keeping, a modern SSD spends most of its life doing very little. Enterprise-oriented drives are more frequently used at full tilt, making their idle power numbers far less important. But this just isn't the case on the desktop, where the demands of client and consumer computing leave most SSDs sitting on their hands for long stretches of time.

The EVO's MEX controller pulls active idle consumption even lower, dropping to under one third of a watt.

PCMark 7 Average Power Consumption

If we log power consumption through a workload, even a relatively heavy one, we see that average use is still pretty close to the idle numbers. Max power may spike fiercely, but the usage seen during a PCMark 7 run is pretty light.

During the run, each tested drive drops from peak to idle over and over again. Often, those peaks correspond to drive capacity; the more flash in a given SSD, the higher we see power consumption reach.

Averaging out power use during a PCMark run can give us a more accurate look at what a moderate desktop workload looks like with regard to power. Again, we observed higher-capacity drives consuming more power during a run, while smaller SSDs rise to the top. 

Maximum Observed Power Consumption

There isn't much to say about maximum observed power consumption. It doesn't warrant a lot of explanation, aside from the fact that few client workloads trigger these levels of use. It's a much more important metric in enterprise applications, where maximum consumption is a critical variable in total cost of ownership.

Periods of high power use happen occasionally, but only briefly. Idle power figures are more representative when it comes to picking an SSD that's going to help extend your notebook's battery life, though maximum numbers that reach too high are worrisome as well.

The 840 EVO has a throttling mechanism to keep temperatures and drive health in check during the most taxing, heat-intensive situations, though we wouldn't recommend testing those boundaries.

14. A Look At Samsung Magician's RAPID Feature

RAPID is a software-based feature in Samsung's most recent build of Magician. Simply, it uses a gigabyte of system memory for caching hot data. Frequently-used applications are stored in RAM, ideally yielding much faster accesses when that data is needed over and over. Unlike other RAM-based caching solutions, RAPID keeps cached data persistent between reboots by writing information to the SSD itself.

The software is only available in the next version of Samsung's Magician. But by the time 840 EVOs are available, the necessary build should be downloadable. We got our hands on an early version, and although we didn't have much time for testing, we did run some preliminary numbers.

The only requirements are a compatible SSD and Magician 4.2. With those satisfied, click the "Enable" button to reboot your system. Once Windows loads, the driver starts up automatically. Of course, this means you're not accelerating the boot process. But with a fast SSD under the hood, this isn't something we were concerned about. 

You might have missed the orange text at the bottom of our Magician screen capture, but RAPID is specifically prevented from interacting with multiple drives. It's not clear whether this is an artificial or truly technical limitation.

The quickest way to verify that RAPID is on and working is to run a canned benchmark. Magician has its own test module, but we went ahead and used CrystalDiskMark for verification. Here's the "before" shot of a 250 GB 840 EVO on a Haswell-based test platform.

Now, for the RAPID-enabled shot:

The performance increase is profound. Writes shoot up, while the read results shoot up as well. But we still had to wonder if RAPID was just a marketing gimmick tacked on to a comprehensive management suite. Without much time to delve into the specifics, we chose one workload that's indicative of real-world performance, since it actually derived from real-world performance: our Storage Bench v1.0 trace with RAPID enabled.

250 GB 840 EVO
Average Data Rate
Mean Service Time
Mean Read Service Time
Mean Write Service Time
RAPID Disabled
279.54 MB/s
512.23 us
237.57 us
1171.1 us
RAPID Enabled
325.96 MB/s
252.02 us
261.32 us
229.55 us

Crazy, right? The Average Data Rate jumps from 279 MB/s up to a record 325 MB/s. Mean Service Time (including read and write I/O times combined) drops in half, which is stellar. Read service times actually slide back a bit, perhaps from the overhead incurred when requested data isn't in the cache. But the mean write service time gets the biggest bounce. The reduction there is just awesome.

I'm convinced we need to take a closer look at this in the days to come. For instance, it's not clear if the extra cache layer is problematic in the event of power loss. After all, with RAPID enabled you have the DRAM cache, the SSD's DRAM, the Turbo Write buffer, and then the triple-level-cell storage itself, creating a fairly complex hierarchy.

15. Samsung's 840 Was Good; The 840 EVO Is Better

Samsung's 840 EVO will be supplanting the company's first triple-level-cell-based SSD when it surfaces next month. The 840 EVO is more than just higher-density NAND, a faster controller, and some new firmware. But it's not completely new either. Rather, we're looking at something in the middle, sporting a more advanced feature set better able to turn heads at value-oriented price points.

A controller clocked 100 MHz quicker and 19 nm flash aren't even the 840 EVO's most notable features. That honor goes to Samsung's Turbo Write technology, which it uses to effectively increase the SSD's write performance in common desktop workloads. Carving out a certain quantity of triple-level-cell NAND to operate as an SLC cache means that dedicated space should outlast the rest of the drive's flash memory many times over. Samsung is clearly confident in the technology. After all, it's protecting the 840 EVO with three-year warranty coverage.  

You should be able to buy the 840 EVO in a couple of different packages. One will be the drive on its own, which allows Samsung to hit the same price point as its outgoing 840. The company is also planning a complete upgrade package to include a USB 3.0-to-SATA adapter and 9.5 mm Z-height spacer. If you plan to clone your hard drive and then use it as an external storage device, that adapter is a very handy add-on.

Samsung's Magician software is already potent. Continued development is extending its usefulness, too. The next best utility package is Intel's venerable SSD Toolbox. However, Intel isn't value-adding nearly as much functionality. While it's true that most mainstream customers won't even bother installing Samsung Magician, we know it to be invaluable for testing, updating, and optimizing our solid-state hardware. Moreover, the inclusion of RAPID and drive cloning enable capabilities you'd have to otherwise pay for separately. Here in our lab, Samsung's bundle includes the niceties and necessities we use every day for testing and maintaining benchmarking platforms.

One important feature that isn't enabled yet, but will eventually make an appearance, is higher-end data security. Once upon a time, powerful encryption wasn't a priority in the client space. But we've read enough news over the past couple of months to make FDE a more interesting prospect. Samsung is planning a firmware update for the 840 EVO will enable this.

Because we're enthusiasts and enjoy the fastest of pretty much everything, we already know that Samsung's 840 EVO isn't all things to all people. However, it's a product able to satisfy most people, armed with features that they'll both want and use. And Samsung plans to ask a price that millions of customers have already paid for vanilla 840s. With the addition of 750 GB and 1 TB models, the company's mainstream SSD family is pretty darned complete. Left with little else to ask for from an SSD, we're pleased to confer the Tom's Hardware Smart Buy award on Samsung's 840 EVO.