With high speed comes great responsibility. Responsibility to make use of that speed wisely. So while solid-state storage can be intrinsically very, very fast, it needs a suitably quick connection to realise all that performance.

And that’s where the most common internal disk interface, second-generation SATA 3Gbit/s, is starting to show its age.

In Crucial’s last SSD, the award-winning Crucial RealSSD C300, we saw Crucial fit the then-cutting edge SATA 6Gbit/s bus to unlock its superb sequential read and write speeds. That was then; now we have even quicker drives.

Here we have a revised take on that same drive in the Crucial M4. Confusingly, it goes under two names: as well as Crucial M4, it’s also known as the Micron RealSSD C400.

The dual branding is down to the two-pronged marketing of one of the world’s major silicon fab works, Micron Technology.

It sells under the consumer names of Crucial (best identified by its extensive RAM portfolio) and Lexar Media (familiar for its USB thumbdrives), alongside its main Micron enterprise division, manufacturing DRAM and industrial solid-state storage.

Technology

When we first reviewed the Crucial C300 it excelled through its speedy Micron flash silicon, fabricated at 34nm lithography, with a generous 256MB of cache; all under the control of a clever Marvell controller chip to handle the, literally, crucial I/O traffic management and internal data supervision.

In the Crucial M4, we see the same large buffer and a near-identical Marvell 88SS9174 controller. The main change lies with the actual NAND flash, which has been shrunk to a 25nm process. And that’s how Micron/Crucial has eked out extra speed. How much more? In some respects, quite a bit more.

Lab testing

To get a good overview of the changes between C300 and C400/M4, we put the former through its paces again on our current PC benchtest workstation, before moving to the new Crucial M4 drive.

In both models, we used the 256GB capacity version.

The new headline sequential read/write speeds of the Crucial C300 as measured by ATTO Bench 32 were 348 and 238MB/s respectively. Those are quick results – but not as quick as the 438 and 281MB/s turned out by the Crucial M4.

Similar numbers unfurled in CrystalDiskMark 3.0, where the Crucial C300 showed reads at up to 356MB/s and writes at 233MB/s. Moving across to the Crucial M4, these numbers rose to 414MB/s for reads and 274MB/s for writes.

Turning the attention to the smaller file exchanges as measured by CDM, we saw a small trade in performance. For 4kB files, read speeds dropped from 33MB/s to 23MB/s between drives, while small writes rose fractionally from 89MB/s, to 90MB/s on the Crucial M4.

A similar write-centric change was observed in the 4k QD32 test (4kB at a queue depth of 32). The older drive reported reads here of 244MB/s and writes of 205MB/s – both amazingly fast results – where the newer M4 was benched at 167MB/s for reads but 244MB/s for writes.

Ins and outs

In professional server applications, the real-world performance of storage devices is often related by the number of input/output operations per second (IOPS). Here we saw some clear gains again for the Crucial M4 – particularly when multiple threads were stacked up.

The AS SSD benchmark test showed that the older Crucial C300 could notch up 7.5k and 18.3k IOPS in simple 4kB read/write transfers; rising to an impressive 56.4k and 45k IOPS in the 4k-64 thread test.

The Crucial M4 reported only around half as many read IOPS in the straightforward 4k test (3.6k versus 7.5k), while writes here were effectively the same at 18.3k versus 18.5k.

But in the 4k-64 thread test, the newer drive nearly doubled in these write characteristics, from 45k to 84k. Reads were somewhat lower though, down from 56k to 40k.

Another very fast 6Gbit/s SATA SSD that launched recently, the Plextor PX-256M2S – which hit even faster 483MB/s sequential reads in our testing – had maximum IOPS here of just 17k/11k for reads/writes.

Drive longevity is a concern for all solid-state storage; more so with the smaller die process that’s appearing. Crucial lists the M4 as able to support 2TB of writing – otherwise expressed as 40GB every day for five years.

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Proving that the latest generation of solid-state drives is faster and less expensive than its predecessor, the Crucial M4 SSD boosts read and write performance.

Solid-state drives have had their share of ups and downs in the past few years. Although SSDs are definitely faster than their mechanical counterparts, they've yet to live up to the performance their specifications suggest. What's more, they can be at least eight to 10 times as expensive as their mechanical equivalents - putting them out of range for the lower-end consumer market. Periodically, though, new SSDs are released that incrementally raise the performance bar while lowering the price barrier. The latest in the series of evolved drives is the Crucial M4 (also called the Micron C400 - Micron Technology is Crucial Technology's parent company).

Crucial M4: The nitty-gritty

Micron builds its own chips for the Crucial M4 using a 25mm die. This is important for two reasons. First, the shorter the internal pathways are inside a chip, the faster data moves without actually changing the speed at which the chip operates. (If you can walk 4 miles per hour, it will only take you a half hour to walk two miles.)

The second is a simple matter of probabilities: In every fabrication process, a certain number of the chips on a wafer are bad. The more chips a manufacturer can build on a wafer, the higher the yield of good chips it can produce at the same cost. This means it can lower the price per chip because of the better yield - offering the buyer both speed and price improvements over its predecessor.

The Crucial M4 boasts sequential read speeds up to 415Mbps and write speeds as high as 260Mbps. That's a significant improvement over Crucial's last-generation RealSSD C300, which had sequential read and write ratings of 355Mbps and 215Mbps, respectively,

Regarding price, the Crucial M4 comes in three versions: 64GB (around £89), 128GB (around £169) and 256GB (£349). Those are the retail prices; I reviewed the 256GB model.

This may seem expensive when you can buy a 3TB mechanical hard drive for half the price. However, if you compare it to other 256GB SSDs, you'll find that the Crucial M4's suggested retail price is competitive with Kingston's SSDNow V100 and Corsair's Performance 3 Series.

Crucial M4: Performance

I first tested the Crucial M4 with the HD Tach benchmark and wasn't impressed by its performance profile. Neither the sequential read speeds nor the burst speeds gave it more than a nominal advantage over the most recent generation of SSDs. It's important to mention, however, that HD Tach is an old, tried-and-true test. However, because it's old, it might not be the best performance indicator for an SSD.

I then tested the Crucial M4 using FutureMark's PCMark Vantage benchmark, which measures performance in 64-bit systems. In this venue, the M4 racked up a 28,668 result, which is nearly 50% higher than SSDs I've tested in the past.

The final series of tests were from ATTO Technology's Disk Benchmark, which measures a storage system's performance with various data packet transfer sizes and run lengths for reads and writes.

Typically, hard drives of any ilk will show a significant preference for reads over writes. This dates back to data handling for transactional databases, where it's more important to retrieve information and have it on the screen while talking to a customer than it is to write data back to the drive. Today, especially for mainstream drives, writes have increased in importance for video and graphic rendering and for music, video and image uploads.

According to the ATTO results, the M4 is more balanced in its read/write performance than the last generation of SSDs. There's still a read preference, but Crucial has done a better job of equalizing the performance between its read and write operations than I've seen in the past.

Crucial M4: Finding its place

If you're looking to upgrade your drive or drive array, it's important to know that you're getting a better bang for the buck. I compared the Crucial M4's test results against those from last year's 256GB Western Digital SiliconEdge Blue (256GB) (representing the previous generation of SSDs) and found that the M4 is significantly faster.

As for its place among the current generation of SSDs, that's a bit more difficult to determine. SSDs within the same generation and price bracket as the M4 would probably only show incremental differences at best. It would be an important comparison if you needed absolute maximum performance, but generally, testing for this would be an intellectual exercise outside of that parameter.

The Crucial M4 has significantly increased the performance gap between it and the previous generation of SSDs. And by pushing write performance - for video capture and editing, graphical imaging, etc - the M4 provides an economical option for disk-intensive environments.

Bill O'Brien, Computerworld US

See also: Group test: what's the best SSD?

Crucial M4: Specs

  • 256GB solid-state drive
  • 2.5in SATA 6Gb/s
  • 256MB Micron DDR3 cache
  • Marvell 88SS9174- BLD2 controller
  • 16 x 25nm NAND flash storage chips
  • specifice endurance 2TB = 40GB per day for 5 years
  • power consumption 150mW (active), <85mW (idle)
  • SMART
  • TRIM support
  • 100.5 x 69.85 x 9.50mm
  • 75g
  • 3-year warranty
  • 256GB solid-state drive
  • 2.5in SATA 6Gb/s
  • 256MB Micron DDR3 cache
  • Marvell 88SS9174- BLD2 controller
  • 16 x 25nm NAND flash storage chips
  • specifice endurance 2TB = 40GB per day for 5 years
  • power consumption 150mW (active), <85mW (idle)
  • SMART
  • TRIM support
  • 100.5 x 69.85 x 9.50mm
  • 75g
  • 3-year warranty

OUR VERDICT

From the lab tests, the Crucial M4 displays clear improvements over the Crucial C300 – in most key respects. The headline-grabbing speeds are indisputably superior, up to 438MB/s read speeds in our tests and 281MB/s when writing. Small file transfer characteristics are less eye-catching but absolutely key to smooth PC operation. And here we saw improved write speeds, but slightly reduced reads. In the context of either of the Crucials’ great small file performance though, we haven’t seen any SSD with the Crucial M4’s terrific sequential speeds, tempered with such consummate small-file transfer juggling and high IOPS. This Crucial M4 SSD easily takes the crown as best SSD we’ve seen and comes highly recommended – especially given its price drop from the C300 of last year.

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