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The Crucial M550 SSD Review: Striking Back With More Performance

Introducing Crucial's M550 Performance SSD Family

The more time we spent with Crucial's M500, the more we appreciated it. It wasn't super-fast by most accounts, but like the m4 that came before, the M500 helped pull SSD prices down to never-before-seen levels. I remember being particularly happy to see M500s going for about $0.50 per gigabyte.

Samsung's game-changing 840 EVO was the M500's first real competitor, boasting a comparable feature set, a similar price, and stellar performance. Whereas Crucial arms its SSD family with 20 nm NAND capable of storing two bits per cell, the 840 EVO employs three-bit-per-cell flash. At least on paper, Samsung was the one at a disadvantage. However, the company uses a number of techniques to overcome its memory's inherently slower performance. As a result, the M500 and 840 EVO lock horns at the top of most recommendation lists. Just look at the top sellers on Amazon's Internal Solid State Drive page; you'll often see the top eight or nine spots monopolized by Crucial and Samsung.

Frankly, I'm not surprised. Both companies know that driving SSD adoption requires mainstream support, necessitating attractive prices. For Samsung, that means evolving its triple-level cell technology. Crucial, on the other hand, is pushing the benefits of its MLC memory and advanced manufacturing. The pair similarly serves up three-year warranty coverage. But after Samsung introduced the 840 EVO with its Turbo Write feature, essentially creating an internal SLC-like cache to improve write performance, Crucial found itself behind in a number of our benchmark charts.

If you're Crucial one year later, how do you strike back? Where do you go after the M500, already such a compelling piece of hardware? How about adding an even faster option to the portfolio called the M550?

The M550 is mostly the same as the M500. Except, whereas the M500 is clearly a value-oriented play for folks looking to emphasize big solid-state capacities, Crucial's M550 is massaged to serve up higher-end performance. It's built with the same IMFT L85 20 nm flash, on the same PCB, equipped with the same capacitors for power-loss protection, and backed by the same DRAM cache at each capacity point. Physically, the main difference comes down to an evolved controller.

This is the first SSD we've opened up with Marvell's 88SS9189 processor inside. It's an improvement over the M500's 88SS9187, designed with the new realities of storage over SATA in mind. Power management is more advanced through features like DevSlp and lower idle consumption. I suspect that there were some performance-oriented tweaks as well, facilitating the M550's speed-up. 

Crucial maintains the M500's same range of capacities. This time around, however, the company isn't relying on as much over-provisioning (that space was primarily used for a cross-die redundancy feature called RAIN). So, now the advertised sizes are binary. Instead of 120 GB, for example, you get 128 GB. Along the same lines, M550s will also be available in 256, 512, and 1024 GB form.

Crucial M550128 GB256 GB512 GB1024 GB
ControllerMarvell 88SS9189-BLD2
NAND64 Gb density, Micron 20 nm L85 ONFi128 Gb density, Micron 20 nm L85 ONFi
Die Count16323264
DRAMMicron LP DDR3 128 MBMicron LP DDR3 512 MBMicron LP DDR3 512 MBMicron LP DDR3 1024 MB
Max Seq Read/Write (MBs)550 / 350550 / 500
Max 4 KB Read/Write (IOps)90,000/75,00090,000/80,00095,000/85,000
Part Number (SATA)CT128M500SSD1CT256M500SSD1CT512M500SSD1CT1024M500SSD1
Part Number (mSATA)CT128M500SSD3CT256M500SSD3CT512M500SSD3N/A
Part Number (M.2 2280)CT128M500SSD4CT256M500SSD4CT512M500SSD4N/A

That pricing info is manufacturer-suggested. Crucial expects the M550 to retail for 15 to 20% more than the M500, but with the 240 GB M500 selling for just $120 in some stores, I suspect that post-launch pricing will drop quite a bit. Of course, some vendors probably plan to capitalize on the M550's newness at first. And like the M500, M550s will ship in M.2 and mSATA form factors as well. Pricing on those could vary, too. 

A glance further up the specification table suggests some fierce performance claims. One criticism of the M500 was that Crucial should have used 64 Gb dies in the 120 and 240 GB models. Samsung did this with its 830, arming lower-capacity models with 32 Gb die and the largest version with higher-density parts. As such, the smaller drives had more dies for interleaving operations, benefiting their benchmark results. Now Crucial follows suit, so the 128 and 256 GB M550s should behave a lot like the 512 and 1024 GB offerings.

Otherwise, the M550 inherits its predecessor's feature set, including support for encryption standards like Microsoft eDrive, TCG Opal 2.0, and IEEE-1667. Thermal protection is part of the package, as is RAIN, Crucial's NAND parity system for protecting against the failure of a flash element. Without a technology like RAIN, losing just one part of a die could kill an entire SSD.

The M500 couldn't overcome an entire die failure. Fortunately, that's a rare occurrence. It could instead spring back from something less dire like the loss of one plane in a die, recovering in much the same way as a RAID 5 array. We know from talking to engineers at Micron that the M500 used 15 NAND elements to each parity block, meaning one-sixteenth of the drive's flash was reserved for parity information. So, 32 GB of the 480 GB model's on-board flash was set aside.

The M550 gets away with using less spare space. It hits similar reliability targets without the reserved NAND thanks to refinements and knowledge gained from the M500. Back when that SSD surfaced, its 20 nm flash was fairly new, and RAIN was necessary. Purportedly, the M550 achieves its better performance, improves reliability, and lets you hold onto more usable space.