If I was upgrading a laptop or desktop computer with a solid-state drive, I'd buy a Samsung 840 EVO SSD in either 250 GB (~$190) or 500 GB (~$370) sizes, depending on the exact setup. Using a new caching tech, it can write up to 2x faster than its similarly priced predecessor.
(Note that ultrabook and MacBook Air/Pro owners might have to choose our alternative picks below.)
The Samsung 840 EVO is one of the best values in solid-state drives right now: the drives are super-fast and they’re priced aggressively. Plus, Samsung has a reputation for reliability that a lot of other vendors lack. The 840 EVO isn’t the fastest SSD out there (but it’s close), and it’s not for everyone. But I think it’s the best option for most people who are upgrading a laptop or desktop. If you spend less, you’ll get drives that are slower, and you won’t save that much money. If you spend more, you’ll get a little more speed and a lot more endurance, good for enterprise servers and people who do professional video editing or other write-intensive work. Still, the vast majority of people will be fine with the endurance of the Samsung 840 EVO. This is the sweet spot in solid-state drives, and for the first time ever, the higher-capacity versions are around the same value as the smaller sizes.
Who Should Get This?
Someone with a computer that is one or two years old, with a traditional hard drive, that they plan on keeping for at least another year. (There’s no sense in upgrading a machine that you’re about to replace, unless you know you’ll be able to bring your SSD with you to your next computer.) Someone who has already upgraded their RAM to 4 GB or 8 GB but wants their laptop to boot, launch programs and load files faster. Someone whose laptop is from 2010 or later. If your computer is older than that, depending on the computer, you may want to start saving for a new computer rather than get an SSD. It all depends how much more life you think you can get out of it.
This also works for someone who wants a good boot SSD for their desktop to complement a larger mechanical drive for storage.
What Size Should You Get?
You should get a 256 GB SSD if…
You have less than $200 to spend
You use streaming media (Spotify, Google Play, Netflix) more than local media, or you don’t mind keeping your music and videos on an external drive.
You don’t deal with large, local data files for work
You’ll be pairing it with a big hard drive for storage (e.g. you’re buying for a desktop)
You should get a 512 GB SSD if…
You can afford to spend about $340
You have one computer, and it’s a notebook with one drive slot
You work with large data sets, or you keep a lot of music and movies on your drive
You should get a 1 TB SSD if…
You need it
You can afford it
The process of loading and writing data and programs from your hard drive is slow but on a SSD it’s very fast. If you’ve never had one on your computer before, prepare to be amazed.
Solid-state drives don’t have any moving parts, unlike traditional hard drives. They’re better than standard hard drives in every single respect except for two. Again, they’re much faster—three or four times faster in sequential reads and writes, and hundreds of times faster in random access—how long it takes to access any given bit of memory. They use less power, put out less heat and don’t vibrate.
Everything you do that requires data on your hard drive (which is a lot of stuff) is much faster on an SSD.
Everything you do that requires data on your hard drive (which is a lot of stuff) is much faster on an SSD. If you have a computer with a standard hard drive, that hard drive is probably the slowest part of your system, and the rest of the computer has to wait around for information to be read from or written to the drive. SSDs are much faster—in fact, they’ve almost outgrown the interface that connects them with the computer.
The current generation of SSDs is pretty close to maxing out the bandwidth of the current 6Gigabit/s SATA interface, with the best performers getting well over 550 MB/s in read speeds and and 400 MB/s in writes. The theoretical maximum bandwidth of this generation of SATA interface is 6 Gb/s, which translates to 750MB per second, but the SATA protocol has some overhead so 600 MB/s is pretty much the best case scenario.
Much more importantly, SSDs have super-fast random access times. Random access measures the amount of time it takes for the drive to access a random bit of data on the drive. A mechanical hard drive has to physically move a magnetic head to a specific part of a rotating disk to read the data; this takes an average of around 17ms on a really fast mechanical drive. An SSD has random access speeds of .1ms. That’s so much faster; that speed really adds up.
Which SSD you have matters, but not as much as just having any decent SSD compared to a standard mechanical hard drive. There are differences in speeds between modern SSDs, but most people will never notice the difference between a top-end SSD and a mainstream SSD from the past year or so. You’ll definitely notice a difference between a SSD and a mechanical drive.
The only problems? SSDs are more expensive per gigabyte than mechanical drives, and right now the most capacious standard hard drives can hold more data than the most capacious SSDs. You can get a 4 TB desktop drive for four cents a gigabyte and a 1 TB laptop hard drive for eight cents a gigabyte. The 1 TB Samsung 840 EVO SSD is $600. The 1 TB Hitachi Travelstar 7K1000 is $90. That’s a huge amount of storage for not much money.
SSDs have gotten much cheaper in the past couple of years, and prices are still dropping. The average price per gigabyte for a decent SSD was $3 in 2010 and $1 in late 2012. Now even the fastest SSDs are under $1/gigabyte.
In early August 2013, the 250 GB Samsung 840 SSD was selling for $175 on Amazon. The 840 EVO is launching at the same MSRP as the original 840—$190 for the 250GB version—but will sell for lower as long as Samsung can keep up with demand.
What To Look For In A SSD
For a desktop or a laptop, I’d recommend a 6 Gb/s SATA SSD with at least 240 GB of space. (Due to the way that different SSD controllers allocate space, these drives can range from 240 GB to 256 GB on the label.)
If you’re a desktop owner, you’ll want to pair your SSD with a high-capacity hard drive like this 4 TB drive, where you should put the stuff that takes up a lot of room but doesn’t benefit from the speed boost of an SSD—stuff like pictures, music and movies. You’ll install your OS and programs onto the SSD and then move your user libraries(Documents, Music, Pictures, and Videos) to the hard drive.
For a notebook, though, you usually only have one drive slot, so capacity is more important. That one drive has to hold everything you keep on your computer. So you may want to consider getting a bigger SSD, like a 500 GB version or larger. As cloud services and streaming become more ubiquitous, the amount of stuff you keep on your laptop will go down, but you’re still gonna need local storage for some things.
How We Picked
Finding a winner wasn’t as hard as one might think given the dozens of makes and models available. That’s because there are several dedicated reviewers who have tested the living daylights out of every last one of them. With that in mind, our first step was talking to the reviewers.
An interview with AnandTech’s Kristian Vättö, one of the best SSD reviewers out there, was particularly insightful when we wrote the first version of this piece in early 2013. He considered brand reliability and price to be more important than straight-out performance, and recommended going for the drive in the sweet spot of performance and value. We also got an opinion from Anand himself when we updated this guide for August’s launch of the Samsung 840 EVO.
I set to reading reviews from the SSD reviewers I trust: AnandTech, Tech Report, CNET, Maximum PC, Storage Review and a few others. Most of the reviews I read, as well as the interviews, were done in March when I wrote the first version of this piece; in July when I updated it for the 840 EVO I read reviews on all the drives that had come out between then and now—the Seagate 600, SanDisk Extreme II, Crucial M500, and more.
The SSD I’d Get
If I was upgrading a notebook computer or buying the primary drive for a desktop, I would get the 250 GB Samsung 840 EVO SSD for about $190, or the 500 GB version if I could afford to spend $370. Not only does it offer the same great value as its predecessor (our previous pick), it’s faster in many cases, thanks to some clever engineering tricks that we’ll cover in detail later, but for now, suffice it to say it costs the same as the last generation SSD from Samsung, but it can be in some cases up to 2x as fast in writes.
It’s faster than any other drive in its price range, and faster than a lot of more expensive drives, too. Virtually every SSD reviewer recommends it as a mainstream pick, even the ones who are extremely enthusiast-focused.
The 840 EVO is cheap enough that there’s no excuse to buy a slower drive from any manufacturer.
The 840 EVO is cheap enough that there’s no excuse to buy a slower drive from any manufacturer. It’s also a better value than drives that are meant to last longer (for enterprise or pro users) or are faster but much more expensive. The 840 EVO is Samsung’s update to our previous favorite SSD, the Samsung 840 Series. Like the 840, the 840 EVO uses TLC NAND and a triple-core processor alongside DRAM cache. The EVO’s processor is clocked faster (400 MHz vs 300 MHz), it uses smaller transistors, and it has a cool caching system that makes it write much faster than the old version. Basically, the 840 EVO is faster and better all around than the 840, except in some things where it’s merely as good as the already very good 840. In fact, it’s very nearly as fast as the Samsung 840 Pro, our step-up model. It’s the SSD to get for most people. And it comes in sizes up to 1 TB, though most people will be fine with the 250 GB or 500 GB versions.
The original 840 was fast, but had a minor weakness: sequential write speeds were a lot slower than those of more expensive enthusiast drives. The 840 EVO has a couple of tricks up its sleeves that puts it close to the same performance level as the fastest drives on the market, which usually sell for at least $40 more (~20% more) at the 250 GB level.
The first is TurboWrite, a built-in cache system that increases write speed by setting aside a small chunk of storage space to act as a super fast buffer. This is in addition to the onboard DRAM cache.
Secondly, there is RAPID, an optional piece of software that diverts extra CPU power and idle RAM from your computer to boost the drive’s performance.
All you need to know is that they make the EVO much faster than its predecessor, but in case you’re curious and really want to get into the technicalities of TurboWrite and RAPID, see the footnote below.
People are really excited about this thing, and one reason is that if you opt for that size, it’s one of the first really good, affordable 1 TB SSDs—the other being the Crucial M500. One whole terabyte is more than most people need in a main laptop drive, especially at $600, but man, SSDs have come a long way really fast, and if lack of capacity is the one thing that’s been holding you back from buying an SSD, you’re out of excuses.
Another great reason to get the 840 EVO if you run Windows: the SSD Magician software that comes with it. Not only does it let you use the RAPID mode I talked about earlier, but you can also see details like how much total data you’ve written to the drive, which is a useful indication of the drive’s expected lifespan. You can also perform firmware upgrades, manual maintenance and more, and it includes drive cloning software to help you move your stuff from your old hard drive. It’s a huge added value.
A minor bonus of the 840 EVO, like the previous 840, is how power-efficient it is. The drives draw just around 45 mW while sleeping, .3 W while idle, less than 1 W on average when they’re in use, and under 4 W at their maximum power draw, according to testing by Tom’s Hardware and AnandTech. That’s low compared to many other drives, which use about half a watt at idle and four or five watts or more at full load. (See the charts on the preceding two links for details.)
The EVO 840 Is Great, But You Don’t Have To Take Our Word For It.
Anand Lal Shimpi of AnandTech, one of the best sources for SSD reviews, says, “I’d have no issues with one of these drives in my system even as primary storage. The performance story is really good (particularly with the larger capacities), performance consistency out of the box is ok (and gets better if you can leave more free space on the drive) and you’ve got Samsung’s firmware expertise supporting you along the way as well. To say that I really like the EVO is an understatement. If Samsung can keep quantities of the 840 EVO flowing, and keep prices at or below its MSRP, it’ll be a real winner and probably my pick for best mainstream SSD.”
Tom’s Hardware, which leans toward the enthusiast desktop PC user, did a big in-depth test of the EVO and says: “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.”
The Tech Report says, “If you’re shopping for a higher-capacity drive for a desktop or notebook PC, the 840 EVO is one of the best options on the market. The price per gigabyte falls as the capacity increases, so you’re getting even more value as you move up the line to the 1TB top model.”
Cnet’s Dong Ngo gave the 1TB version an Editor’s Choice award, saying “At the current price of well under $1 per gigabyte — the 1TB capacity costs just $650, or about 65 cents per gigabyte — the Samsung 840 Evo is the best deal on the market now, ranking at the top of the current best SSD list. If you’re looking for an SSD to upgrade your computer’s hard drive with or want to upgrade your existing SSD to a larger-capacity drive, the 840 Evo is as good as it gets.”
Can You Get A Cheaper 512 GB SSD? Not Really.
You might consider going with a slower, older 500GB-range SSD to keep your costs down. We would, too, in theory, if you can find a cheaper 500 GB drive than a Samsung 840. For example, the 512 GB Crucial m4, a drive that has been out for several years, is $370 on Amazon while the 500 GB first-gen Samsung 840 is $340. That said, if you see one of the good competitors below selling for cheaper than a Samsung 840 or 840 EVO, snatch it up.
Some Detailed But Minor Differences On The 500 GB, 750 GB And 1 TB Versions Of The Samsung 840 EVO
We recommend SSDs in the 250 GB range because they’re cheap enough for most people to afford and capacious enough for most people to use. But, as mentioned above, 250 GB isn’t enough for everyone, so you’ll want to consider getting a larger drive if you can afford it.
The higher capacity Samsung 840 EVO drives aren’t just bigger than the smaller ones. There are some other differences as well: Performance, endurance and price. The first two are specific to the fact that, as explained below, the 840 series SSDs use TLC NAND instead of the more common (and more durable) MLC NAND. Here’s the in-depth explanation, but the upshot is that on an SSD with TLC NAND, the 500 GB version should last roughly twice as long as the 250 GB version (and the 1 TB version will last twice as long as the 500GB version). That’s irrelevant for most of us. More relevant is the fact that, because of the specific controller used in the 840, the 500 GB and 1 TB drives actually have faster write speeds in some tests than the 120 GB and 250 GB versions–close to 100 MB/s faster in some tests.
So the bigger one isn’t just bigger, it’s also faster and more durable. The third part is price: The 500 GB version is about $370—what you’d have expected to pay for a fast 250 GB SSD a couple of years ago. In the past, most drives’ dollar-per-gigabyte value actually decreased at higher capacities, but right now the 500 GB first-gen 840 is selling for twice the price of the 250 GB 840. The 840 EVO, at least at its MSRP, is a better value at higher capacities. The MSRP for the 250 GB is $190, the 500 GB is $370, and the 1 TB is $650.
The Problem With The Samsung 840 EVO, And Why It Doesn’t Matter
The 840 EVO, like the first 840, is so inexpensive because it uses TLC NAND, a less expensive form of flash memory than the MLC NAND used in most SSDs. It’s less expensive, but it can be written and erased fewer times, and it has slower write speeds. But does that matter?
The first 840 wasn’t as fast as its peers in sustained writes—most noticeable when you’re copying big files to and from your SSD. The Samsung 840’s write speeds stay around 250MB/s for the 250GB drive, which is nearly twice as fast as the best mechanical drives and seven times faster than a USB 2.0 flash drive, but only about 60 percent as fast as the very fastest consumer SSDs.
This is the problem that Samsung addresses with TurboWrite in the 840 EVO, and as long as you don’t overload the buffer your writes are going to be much faster than on the 840.
It’s not really a big deal for most people, because a) most people don’t do a lot of big write operations, and b) if you’re copying big files, unless you’re copying from another SSD, the sequential write speed of the 840 is going to be faster than the read speed of whatever you’re copying from. Video and photo editors do write large files pretty often, as do some other kinds of professionals, so if you’re one of those people you ought to be getting one of the step-up models below, not a budget SSD.
What about durability? Because it’s using TLC NAND, the 840 EVO doesn’t have as long a theoretical lifespan as a drive with the more common MLC NAND, but the chances that you’ll actually wear your drive out before you replace it with a newer one are incredibly low. Each block of TLC NAND can be erased 1,000 times before it stops working, compared to 3,000 times for the MLC NAND found in most SSDs.
How Long Is That In Real World Usage?
As Dong Ngo pointed out in his review of the first 840: “In real-world usage, this lower write endurance is not really a big issue, however. Per my rough calculations, if you write/rewrite about 10GB of data daily, it would still takes about 7 years for a 250GB Samsung 840 series drive to run out of P/E cycles. Most of us don’t write 10GB per day, at least not every day. But heavy users, such as video-editing professionals, should pick a different SSD for their job.”
In his email to me, Kristian said, “Some think the SSD 840 is inferior because it uses lower endurance TLC NAND. However, based on our calculations the endurance is still more than enough for consumers so the concern is mostly invalid.”
The 840 EVO shares the same kind of NAND, but by now the 840 has been around long enough that people aren’t concerned about the lifespan of the TLC NAND. Anand devotes an entire page to discussing endurance on the 840 EVO and concludes by saying, straight up, “Endurance isn’t a concern for client systems using the 840 EVO.”
I picked the Samsung 840 EVO because it’s the new and improved version of our last pick, and nothing has come out since then that can compete with it. It has great-enough performance and an amazing price. But it’s not the only option.
For Video Editors: Samsung 840 Pro
If you edit a lot of video or photos or do something else that’s heavily write-dependent, you may want a top-end SSD like the Samsung 840 Pro, which is available in a $225 256 GB configuration and a $465 512 GB version (there are also smaller ones that probably aren’t worth it for most people). The 840 Pro is one of the fastest drives you can buy, but here’s why normal people should not buy it—it’s only slightly faster than the 840 EVO (which says a lot about how good the EVO is) and costs 20% more than the EVO. The big differentiator is that it uses more durable MLC NAND than the regular 840, which is important if you do a lot of writing to the drive, and it’s backed by Samsung’s reputation for reliability, plus a 5-year warranty. It’s recommended byAnandTech, Maximum PC, CNET, and many more. These are more necessary for professionals and workstations but normal people should just get the EVO in the biggest capacity that makes sense.
I sent Anand Lal Shimpi an email asking his opinion. He replied, “For consumer/client use there are three brands that I’m most interested in these days: SanDisk, Samsung and Crucial.
“If you want the best mainstream drive the 840 or 840 EVO are probably the best bet from a price per GB perspective. I’d recommend the former if you want a good drive below 512GB, while the latter will probably be your best bet if you want a high capacity drive.
“The SanDisk Extreme II is a good option if you want to use something like 90% of total available drive space as it has decent IO consistency. Crucial’s M500 is a good 1TB option if you need an alternative to the 840 EVO that’s slightly cheaper.”
Although the 840 EVO will eventually replace the 840, if you can find a 250 GB or 500 GB first-gen 840 for less money than the EVO of the same capacity, it’s still a good pick. As Anand said, above 500 GB the EVO is a better option.
Crucial’s m4 is one of the oldest drives I’d recommend. It’s never been a top performer, but it’s cheap, speedy enough and reliable. It’s popular, too, with a 4.5/5 average on Amazon from over 1,500 reviews. The Samsung 840 is faster, though, and it’s usually cheaper. The Crucial m4’s warranty is three years—same as the Samsung 840.
The SanDisk Extreme II is a great new contender for the step-up drive. It’s not quite as fast all-around as the 840 Pro, but it’s more consistent. Anand likes it for those reasons, but we’d stick with Samsung because it’s faster if you have some free space left, which you should.
Crucial’s M500 is notable mostly for being one of the few other affordable 1 TB (well, 960 GB) SSDs on the market. It’s mostly slower than the 840 EVO, but—like the SanDisk Extreme II—it has performance that’s consistent no matter how full the drive gets. I’d still stick with the 840 EVO.
The Seagate 600 is also fast and generally solid, though it has higher-than-usual power consumption. Also, Seagate, though one of the two huge hard drive manufacturers, is late to the game on SSDs; they don’t have the long-term reliability reputation yet.
The OCZ Vector and Corsair Neutron GTX are both speedy, with the Vector right up there with the Samsung 840 Pro at the very top of the performance charts and the Neutron GTX not far behind. They’re just more expensive than most people need–the Vector is 30%-40% more expensive than our main pick and the Neutron GTX is about 15 percent more expensive. If price doesn’t matter or you’re buying for a workstation or other pro machine, you could consider them.
Plextor’s M5 Pro Xtreme has good reliability and performance, but not as good as the top-end drives. Dong Ngo at CNET preferred it to the first-gen Samsung 840 (though not to the EVO), giving it 4 stars out of five and praising its performance, but it’s hard to find a good price on one right now, so I’d still get the 840.
Don’t get anything with a 3 Gb/s SATA controller. Even if your computer only has a 3 Gb/s SATA port, it’s cheaper to buy a great 6 Gb/s SATA drive than a mediocre 3 Gb/s drive.
There are dozens of SSDs based on the SandForce SF-2281 controller: Corsair’s Force 3 and Force GT; Kingston’s HyperX, SSDNow and SSDNow V+; Mushkin’s Chronos line, OCZ’s Agility 3 and Vertex 3; OWC’s Mercury Aura, Mercury Electra, and Mercury Accelsior lines; Patriot’s Pyro SE and Wildfire SSDs; SanDisk’s Extreme, and many more.
Don’t get them. The SF-2281 controller is fast, but has a reputation for flakiness after a bluescreen-causing bug was discovered in 2011. The bug has been ironed out now in most drives via firmware updates, but there are lingering issues with the controller and its firmware, so I’m still leery enough of the platform to avoid any drives based on it. With one exception.
I make an exception for Intel’s 330, 335, 520, and 525 Series SSDs, which undergo such thorough validation and run such customized firmware that I’ll give them a pass. From Anand’s 330 Series review: “Of the available SandForce drives, I’ve felt most comfortable recommending Intel’s own. The pass through Intel’s validation labs provides that extra peace of mind that hopefully translates into a better overall experience. In the past Intel has been a reliable option in the market but not necessarily the most affordable.” Not the most affordable is right–Intel drives carry enough of a price premium over the competitors that they’re hard to justify. A 240 GB Intel 520 is $245, which is $15 more than the faster Samsung 840 Pro. The Intel 335 series is a better deal, with an MSRP of $185 for the 240 GB version, but actual prices tend to be closer to the $210 range.
Other Form Factors
I’d still get the 840 EVO, though there’s a little more flexibility in terms of capacity in desktops since you usually have more than one drive.
For laptops with mSATA drives
Fewer companies make mSATA drives than make standard form factor SSDs, but your best choices are the Crucial m4, Plextor M5M or Intel 525. Says Kristian, “I know we haven’t reviewed the M5M yet but I have a sample here and it’s performing nearly as well as the 2.5” M5 Pro. The procedure is again the same, look at the prices of those three SSDs and use it to pick the best option.”
For Retina MacBook Pros, MacBook Airs
Most Macs use the same 2.5-inch SATA form factor as any other computer, so you’ll be fine with the 2.5-inch drives recommended above.
People who have Retina MacBook Pros or recent-model MacBook Airs are going to have a tougher time–Retina MBPs and MBAs use different SSD form factors from other computers, and they don’t even use the same form factors as each other.
You basically have two options for these computers: OWC and eBay. OWC (aka Other World Computing, aka MacSales) is the only manufacturer that makes their own SSDs in Apple’s form factors, which ZDNet says are cheaper and faster than the ones Apple sells. And eBay? As Kristian points out, “You can often find the original SSDs that Apple use, which guarantees no compatibility issues and sometimes they are pretty cheap (owners are getting rid of them since they upgraded their SSD).”
Care And Feeding
As mentioned above, if you’re on a Windows computer you should install the SSD Magician software, to help you keep on top of disk maintenance and firmware updates, and stay aware of the health of your drive. You should try to keep at least 20 percent of your drive space free, to avoid performance slowdowns as the drive fills up. Anand recommends partitioning your drive so that 25 percent of its available space is left as spare area.
Last Year’s Model
If you can find last year’s Samsung 840 for a significantly cheaper price than the 840 EVO (like 30% cheaper) go ahead and snatch it up. It won’t have TurboWrite and RAPID to make the write speeds faster, but the 840 is still a great drive and it’s better to have last year’s best SSD than this year’s best mechanical drive.
That said, you probably won’t find the 840 for cheaper than the EVO; in fact, as I’m writing this the 840 EVO isn’t for sale yet and prices of the 250 GB first-gen 840 have crept right up to the MSRP of the 840 EVO.
If you have a laptop or desktop that’s a couple of years old and either doesn’t have an SSD or has an older, slower, lower-capacity SSD, you should get the Samsung 840 EVO as an upgrade.
If you need an mSATA SSD, get the Crucial m4 (mSATA version), Plextor M5M or Intel 525. If you have a Retina MBP or Air, get something from OWC. Otherwise, get the 840 EVO, and get the 500 GB if you can swing it.
The Samsung 840 EVO takes advantage of Samsung’s vertical integration (fancy phrase meaning “they make everything in it”) and you get a really great speed boost, a drive that’ll last longer than your computer and some money left over. It’s got significant improvements over the last-gen 840, and it comes with some great and useful software. It’s not the only good option, but it’s the one I’d pick.
Let’s cover TurboWrite, which is a hardware thing.
There are two types of NAND flash memory involved here: SLC (single-level cell) stores one bit of information per cell, and MLC stores more. SLC is faster and lasts longer than MLC or TLC, but it’s more expensive and less space-efficient. For this reason it isn’t used much in consumer SSDs anymore. Most SSDs now use MLC (multi-level cell) NAND, and the vast majority of those use two-bit-per-cell MLC—enough that MLC basically means “two-bits-per-cell”. TLC (triple-level cell) stores three bits of information per cell and is more space efficient as a result.
The 840 EVO consists of TLC, which keeps the costs down and capacity high, but by setting aside a certain amount of TLC NAND and running it as if it was SLC memory (that is, only storing one bit of data on each cell instead of three), it’s able to get SLC-like performance for write caching. Setting aside 9 GB of TLC NAND, as with the 250 GB drive, gives you 3 GB of much faster storage, which the drive uses as a write cache—as long as you don’t fill up that buffer, your write speeds are fast. Really fast. It’s like how some technologies, like Intel’s Smart Response Technology, Seagate’s Barracuda XT or Apple’s Fusion Drive use fast flash memory as cache for a slower mechanical drive. Except here, it’s very fast flash being used to cache a flash drive (keep your Xzibit references to yourselves). As Anand says, “It’s this TurboWrite buffer that gives the EVO its improvement in max sequential write speed over last year’s vanilla SSD 840.” As long as the TurboWrite cache isn’t completely filled up by a big write, your sequential write speeds on the 250 GB EVO will be about twice as fast as the first-gen 840. Bigger capacities have more TurboWrite cache, and they also have faster sequential write speeds, so TurboWrite is most useful on the 250 GB version. The 120 GB and 250 GB versions of the drive have 3 GB, the 500 GB has 6 GB, the 750 GB drive has 9 GB, and the 1 TB drive has 12 GB of TurboWrite cache.
RAPID, on the other hand, is a software thing that boosts the EVO to insane speeds by employing idle system resources, but it’s not for everyone.
RAPID is a setting you can enable from Samsung’s SSD Magician software (Windows only, alas) that uses some of your processing power and up to 1 GB of your RAM as an even faster cache for your drive. This gives you truly fantastic read and write speeds—way past the 550 MB/s or so you’d normally be able to squeeze out of a single drive on a 6 Gb/s SATA connection. The downside is that you end up trading CPU and RAM resources for drive speed, so it’s better used on a desktop or powerful laptop, since you’re more likely to have the spare computing power.
Another catch is that using RAPID could lead to data loss in some situations if you’re using a desktop without a backup power supply. Since RAPID caches write operations as well as read operations, it’s possible that you could lose data if the power goes out before the software has had a chance to write a large transfer to the drive. This is a mainly problem on desktops that aren’t plugged into a UPS, not on laptops, but it’s an argument against using the RAPID software.
That said, the 840 EVO is fast even without RAPID and stupid-fast with it. Quoth Anand, “The potential performance upside is tremendous. While the EVO is ultimately limited by the performance of 6 Gbps SATA, any requests serviced out of main memory are limited by the speed of your DRAM. In practice I never saw more than 4 – 5 GB/s out of the cache, but that’s still an order of magnitude better than what you’d get from the SSD itself.”
This guide originally appeared on The Wirecutter on August 14, 2013 and is republished here with permission.