Crucial M550 1 TB full review

Crucial is the consumer-facing division of US semiconductor giant Micron Technology. As a manufacturer of NAND flash, it sits at the high table for solid-state drives, and has been a significant player since the early days of the SSD.

This year’s new M550 model of its 2.5in SATA solid-state drive is a relatively minor revision to last year’s M500. Helping the marketing story, 550 also happens to be the number of megabytes of data that can be read sequentially from the SSD, ‘with all file types’ says Crucial.

See also: Storage reviews

The latter clause is perhaps a gentle but deserved dig at manufacturers that use SandForce controllers, noted for their SSDs’ plummeting write performance when presented with any compressed media files.

The M550 is listed as using 20nm MLC NAND flash again, sourced in-house of course, and there is still a Marvell controller in charge, this time a Marvell 88SS9189 which must be a revised ‘9187 used in the M500.

Other changes should also raise the desirability of the M550 over the M500. Crucial has added a power-reserve capacitor – a trick used in enterprise-class drives – so that in the event of sudden power loss the contents of the large buffer can be saved, and the controller shutdown gracefully. In the case of the largest M550 drive, that’s up to 1 GB of data to preserve. While this may be useful for desktop PCs, we’d contend it’s less essential for laptops – a significant part of the SSD target market – as these already contain a form of UPS in the form of a built-in battery.

We asked suppliers to submit the largest drive they could, since larger capacities are more likely to return the best results, but only Crucial acceded with its first 1 TB drive.

Last year’s M500 was also offered in the terabyte class, available as a 960 GB version, and while it was based on 1024 gigabytes of NAND flash, it conservatively kept more in reserve for over-provisioning. This helps maintain drive health and longevity, and is especially useful for preventing significant slow-downs when an SSD is kept under worst-case continual write operation.

Now Crucial has opened up its largest SSD to make it truly a terabyte in capacity. That was a large size for even regular notebook hard disks, so to see it as an ‘affordable’ option in solid-state form is quite exciting.

While close to £400 is still plenty to pay for a computer drive, in gigabyte-per-pound terms it’s staggeringly cheap for a high-performance SSD. At time of press Amazon UK was selling the 1 TB Crucial M550 for £350, a figure of just 35p per gigabyte. That’s half the price of Intel’s latest 730 Series.


Given the cakewalk test of ATTO Disk Benchmark, the Crucial M550 was indeed able to achieve 550 MB/s read speeds. In fact the highest figures we recorded here were 563 MB/s, that using 512 kB data. But as you may expect, like all current solid-state drives it cannot maintain this speed with smaller data chunks.

From 256 to 8192 kB data, the M550 could indeed keep the ‘550’ pace; but by 128 kB its read speed had fallen to sub-500 MB/s figures, finally settling at 21 MB/s with the benchmark’s smallest 0.5 kB data files.

In CrystalDiskMark the highest numbers we saw were 478 and 464 MB/s for compressible read and write sequential transfers; that already shows a lift in write performance over the M500’s flat-out write figure of 436 MB/s. Random data transferred at the same pace, 483/465 MB/s.

Small-file operations have benefitted on the M550. Single-threaded 4 kB writes were at around the 100 MB/s mark for the M550; and around 30 MB/s for reads. But multi-threaded transfers broke the nominal 100 IOPS ceiling for 4 kB random reads, at 100.0 k IOPS, with writes not very far behind at 91.6 k IOPS. In the AS SSD benchmark, an overall nominal score of 1096 points was the highest of all models tested.

Find the best price

Best prices today

Retailer Price Delivery  

Price comparison from over 24,000 stores worldwide