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Best SSD Group Test: Samsung 840 EVO vs 840 PRO and Crucial M550

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Best SSD Group Test: Why should you buy an SSD?

Solid-state storage used to be reserved for the most expensive PCs, and even the priciest of drives weren’t exactly capacious – you’d be able to install Windows, a couple of apps, and then you’d be back to your hard disk.

It’s 2014, though, and that’s all changed: SSDs serve up hundreds of gigabytes of storage space, and you can get your mitts on this super-fast storage for reasonable prices. These new types of drive are often found inside even mid-range desktop PCs, and nearly every Ultrabook also uses these Flash-based drives rather than older, slower hard disks.

There are numerous advantages to installing an SSD into your PC or laptop. A Windows installation on an SSD will boot in mere seconds rather than the minute or two it can take for an older, neglected hard disk to get ready for use, and applications installed to the SSD exhibit similarly rapid loading times – handy for both work and play.

SSDs can also be smaller than hard disks, which means they’re often able to fit where platter-based drives can’t reach. This makes them ideal for ultra-compact desktop PCs or of course the ever-slimming world of laptops. SSDs also have no moving parts, which makes them tougher and more reliable than traditional hard disks.

Best SSD Group Test: How We Tested

The six drives in this test have been subjected to a rigorous benchmark routine to weed out what’s worth buying and which can be left on the shelf.

Benchmark applications AS SSD and CrystalDiskMark run each drive through a variety of tests. Their sequential read and write routines test the raw file-copying pace of each drive, while a variety of random read and write tests demonstrate how responsive the drive is to the more random use a drive is put through during day to day use – the ‘snappy’ feel of an SSD is all about its random read access performance. ATTO’s benchmark also tests the read and write pace of each drive, but it uses an even larger variety of file sizes, which adds further detail to the picture of how each SSD will perform.

We’ve also run PCMark 7’s storage test, which uses simulations of typical file access patterns of real-world programs to give an indication of how each drive will handle real-world applications. We’ve also taken the temperature of each SSD – if any overheats it’ll be worth knowing, especially if it’ll be used in a confined space.

To help us decide which drive is this month’s best, we’ve lined up their prices and warranties – and taken a look at what extras you get in the box, too.

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Best SSD Group Test: Under The Hood

Every drive in this test ranges in capacity from 240GB to 256GB, so you’ll get a similar amount of formatted space from each SSD and their prices are comparable, too – all are around £100.

There are more differences between these drives when their specifications are considered. Most notable is the Samsung 840 EVO 250GB (£121) drive uses 3-bit TLC (Triple Level Cell) NAND that stores more data in the same space as the memory chips found inside many other drives (which use dual-level cells called MLC), and it’s also moved from 21nm to 19nm chips – a change that should improve performance.

That also means the lifespan on this drive is shortened, at least on paper, although Samsung has tried to combat this by using more of its NAND for housekeeping and preservation duties – which is why this drive is available in rounded capacities like 250GB rather than the more traditional 256GB.

Samsung 840 EVO (left), 840 PRO (right) are available in up to 1TB versions

The Samsung 840 PRO 256GB (£150) drive uses a new in-house controller that’s got three ARM Cortex R4 cores clocked to 300MHz. It’s also got 512MB of LPDDR2-1066 RAM, which is double the amount included in its predecessor, and faster too – although this SSD does rely on older, slower 21nm NAND chips.

The Plextor M6S (£TBC) and Crucial M550 (£115) drives both use dual-core Marvell controllers, which means the two companies have been able to develop custom firmware for their SSDs. Plextor’s drive is its first to move from the standard 9.5mm form factor to 7mm, which means it’s slimmer, better-looking and can fit into smaller spaces such as the latest slim laptops. Crucial’s new M550, meanwhile, has 512MB of RAM – but also uses the same 20nm MLC NAND that was found in its preceding SSDs.

Toshiba QToshiba Q Pro

Little is known about Toshiba’s drives, the Toshiba Q (£126) and Toshiba Q Pro (£112). The 19nm MLC memory used to build the Q and Q Pro drives is made in-house, and Toshiba also makes its own controllers – but that’s all the information available. We do know that while these drives do use the slimmer 7mm form factor, they’re not exactly good-looking: their utilitarian metal cases pale in comparison to the smart, dark Samsungs.

Best SSD Group Test: AS SSD

READ Crucial M550
Toshiba Q
Toshiba Q Pro
Samsung 840 EVO
Samsung 840 PRO
Plextor M6S
Sequential 517.06 509.23 515.57 511.41 521.05 486.88
4K 29.6 20.79 22 36.08 31.7 31.38
4K-64 306.03 292.69 229.85 296.39 304.61 290.21
Access time 0.042 0.082 0.159 0.046 0.054 0.043

Sequential 481.93 487.18 482.85 483.09 500.85 422.18
4K 94.14 82.83 79.93 90.2 85 78.18
4K-64 334.29 192.9 227.59 260.39 323.26 284.84
Access time 0.048 0.039 0.038 0.037 0.04 0.048

This application’s sequential read and write tests are key indicators of an SSD’s performance, so we’re pleased to report that five of the six drives on test returned sequential read scores of more than 500MB/s, with Samsung’s 840 PRO 256GB drive topping the table with 521MB/s. The Samsung SSD didn’t just excel in the read test, either – its 501MB/s score in the sequential write benchmark is similarly impressive, and it’s further ahead of rivals than its read result.

The only drive to disappoint in sequential reads and writes was Plextor’s new M6S 256GB, which was significantly slower than every other SSD in both benchmarks.

The Samsung 8401 PRO kept performing well in AS SSD’s small file tests but, while it was towards the top of our table, it wasn’t the best here: Samsung’s own 840 EVO 250GB was quicker in the 4K run, while Crucial’s new M550 drive was faster in the 4K-64 random file benchmark.

We’ve already mentioned the Plextor’s poor sequential performance, and it didn’t pick up the pace when handling smaller files; it was mid-table at best, but elsewhere came bottom. It was joined here by Toshiba’s two 256GB drives, which weren’t too bad in sequential tests but returned poor, inconsistent results in these smaller file evaluations.

Samsung’s EVO drive was the only SSD to consistently impress in access time tests, but the margins here are tiny – hundreds of milliseconds separate some drives. It’s not something you’re going to notice in day-to-day use.

The Samsung 840 PRO got off to a great start in this test thanks to its impressive sequential read and write performance, but Crucial’s M550 256GB wasn’t far behind – and the M550 beat its more expensive rival in three out of the four small file benchmarks, too. For that reason the more consistent Crucial drive takes the crown in AS SSD.

Best SSD Group Test: CrystalDiskMark

READCrucial M550Toshiba QToshiba ProSamsung 840 EVOSamsung 840 PROPlextor M6S


This application kicks off with another pair of sequential read and write tests, so it’s no surprise that Samsung’s PRO-series SSD was strong here – although Samsung’s own EVO drive was barely three megabytes slower in the read test and less than half a megabyte behind when writing files. The previously impressive Crucial M550 wasn’t as good in these sequential trests: bottom of the table when reading, and mid-table when writing.

The EVO drive overhauled its more expensive stablemate in the 512KB and 4KB benchmarks with table-topping results, and the two drives shared similar 4K-32 random file score.

In the small file write tests, though, both Samsung drives faltered, and the Crucial M550 took the lead. Its 4K and 4K-32 results of 107MB/s and 269MB/s were noticeably quicker than the Samsung drives, and it was the quickest of any SSD on test.

The three other drives in this group failed to impress in this application. Plextor’s factory-fresh M6S was in the bottom half of the table for most of the tests. Toshiba’s drives weren’t far behind the leaders in sequential tests, but dropped off dramatically in small file runs.

The winner, this time around, is the Samsung 840 PRO: its read performance is consistently excellent, and its sequential and 512KB write results are similarly impressive. Crucial’s M550 is better with writing small files, but it’s not enough to overhaul the Samsung.

Best SSD Group Test: Atto Disk Benchmark

Atto Disk Benchmark
READ Crucial M550 Toshiba Q Toshiba Pro Samsung 840 EVO Samsung 840 Pro Plextor M6S
8 175,906 340,836 357,179 386,744 299,155 299,704
32 362,869 375,565 470,890 518,914 526,899 462,409
64 427,932 478,961 474,288 536,870 545,078 496,325
256 545,164 540,275 546,400 541,489 551,402 517,196
1024 559,240 545,354 551,579 555,383 556,663 512,525
4096 563,151 545,354 547,827 556,663 557,948 519,971
8192 563,151 547,827 554,109 556,663 559,240 514,984

8 401,649 366,264 390,840 378,706 386,858 269,808
32 489,443 494,338 496,325 380,887 493,105 351,928
64 505,025 511,245 512,507 512,507 517,619 315,223
256 497,951 509,807 506,192 518,448 480,087 445,894
1024 506,481 519,971 517,465 532,874 488,064 449,553
4096 510,091 518,715 521,233 534,495 486,957 361,123
8192 511,305 518,715 521,233 534,495 473,014 447,392

This testing application delves deep into different file sizes to provide a more granular view of read and write performance, and it’s here that the Samsung 840 PRO’s previously-iffy small file writing performance was exposed.

While the Pro was reasonably quick at writing the smallest of files, its pace eventually hit a limit below 490MB/s and stayed there, while four of the other SSDs here – including the cheaper Samsung 840 EVO – ploughed past 500MB/s. It’s a shame, because the 840 PRO’s read performance is excellent, and is the best on show in three out of our seven Atto runs.

Samsung’s more affordable EVO drive wasn’t just better in the second half of Atto’s write tests – it was one of the most impressive performers in the reading benchmarks, too. That makes this a very consistent drive, which is more than can be said for the M550: it lead the way in the latter three reading tests, but its first three reading tests were bottom of our results table, and it was mediocre in the file write benchmarks.

The new Plextor M6S continued to lag behind: it was the slowest SSD here in eleven out of the fourteen Atto runs. Toshiba’s two drives were fast and consistent when writing, but poorer when reading files.

There’s only one winner in this category, and it’s the Samsung 840 EVO, which is the only SSD on test that’s both quick and consistent.

Best SSD Group Test: Other Benchmarks and Features

The PCMark 7 storage benchmark handles a host of real-world tasks that will be impacted by SSD performance, including importing pictures, editing video, running listening to music, booting applications, playing games and even basic Windows navigation.

It’s an important real-world performance indicator, and the new Crucial M550 took home the crown with a score of 5,623 points. That’s a little ahead of the Samsung 840 PRO, which came second with 5,550 points, and the bronze went to a surprise entrant – Toshiba’s Q-Series Pro, which scored 5,544 points.

PCMark 7

Crucial M550 Toshiba Q Toshiba Q Pro Samsung 840 EVO Samsung 840 Pro Plextor M6S
Storage Test

5,623 5,491 5,544 5,416 5,550 5,394

We have no concerns about any of the SSDs overheating, as all operated at between 27x°C and 35x°C. Samsung’s EVO was the coolest, while the standard Toshiba Q Series was warmest.

It’s not just benchmark results that determine which SSD you should buy – it’s worth taking a look at what comes in the box, too. We’ve seen drives before come with metal 2.5in to 3.5in brackets, SATA cables and even external enclosures, but none of the SSDs in this test are as generous. Crucial’s M550 and the Toshiba Q Series Pro include spacers so these 7mm drives can be used in 9.5mm slots, but that’s it – and Toshiba’s standard Q drives and the Plextor M6S don’t come with any extras.

Neither of Samsung’s drives come with anything extra, either, but the firm does sell laptop and desktop upgrade kits for its EVO drive. The former comes with a spacer and a SATA to USB 3.0 adapter, and the latter includes a USB adapter and a 2.5in to 3.5in bracket, a SATA cable and all the screws required. Both options add around £12 to the price.

Warranties are important, too. At one time many SSD firms offered five years of coverage on new drives, but only the Samsung 840 PRO drive includes that now, indeed that’s it’s key selling point and why it has 'Pro' in its name. Four of the other SSDs on test include three years of coverage, and Toshiba’s standard Q Series languishes with two years.

Best SSD Group Test: Conclusion

Samsung's 840 PRO series drive got off to a great start in our benchmarks, with table-topping sequential speed in every AS SSD and CrystalDiskMark test – and it followed that up by running towards the top of the table in several other benchmarks.

It looked strong, but its inconsistent Atto performance hampered its prospects – and, at £150, it’s the most expensive drive here along with the standard Toshiba Q Series. There’s no denying this drive’s raw speed, but it’s only worth buying if you’re comfortable spending more cash or you know you’ll regularly be writing large volumes of data to it so will need the extra warranty. , too.

The next contender, Crucial’s M550, is a brand-new drive that performed well in many of our benchmarks, and its £114 price makes it the cheapest drive here. It was slow in many of the Atto tests, though, and occasionally fell behind in our other benchmarks.

The Samsung 840 EVO drive is only £7 more expensive than the Crucial, but it’s better in many key benchmarks, with its CrystalDiskMark performance especially impressive. It was the most consistent drive across the board in Atto, too, and led the way in many of these tests – and, in most of the tests where the EVO didn’t top the table, it wasn’t far behind the leaders.

It’s this combination of consistent, quick performance and a keen price that means the Samsung 840 EVO takes home the prize in this test. If you want to super-charge your storage without breaking the bank, it’s unquestionably the drive to buy.

Next, read our best Windows 8 laptops and tablet round-up

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