The Crucial M550 SSD Review: Striking Back With More Performance

RAIN: Protecting Against Small NAND Failures

Last year's M500 really needed Micron's RAIN (Redundant Array of Independent NAND) technology to satisfy the company's reliability requirement. With IMFT's 20 nm process still young, it made the M500 a more resilient product. 

More mature manufacturing lets Crucial pull back on the parity-based redundancy system, freeing up user-accessible space.

In Micron’s magnum opus (Micron RealSSD P320h Review: A PCIe Drive Capable Of 3.2 GB/s), one-eighth of the flash is monopolized by RAIN. Losing all of that space is painful on a PCIe-based drive with 1024 GB of pricey single-level cell memory on-board.

Such a big sacrifice wasn't an option on the desktop-oriented M500, so Micron settled on a ratio of 1:15 instead. The 480 GB model comes with 512 GB on its PCB, so that's 32 GB set aside for RAIN. Normally, a 480 GB drive would use tons of extra over-provisioning to minimize write amplification and improve steady-state write performance. But with the M500's implementation of RAIN, the 480 GB drive still has a standard 7% to lean on.

Given the M550's binary capacity points, the only way to reserve capacity for RAIN and get away with putting 512 GB (for example) on the box would have been adding extra flash, which Micron did not do. Rather, the solution is reducing RAIN’s ratio of parity to storage elements. Instead of 1:15, the M550 rocks a crazy 1:127 relationship. On the 512 GB model, that's still 4 GB of space for RAIN. The 1024 GB version has 8 GB to work with. Naturally, only the smallest flash failures are covered. But the M550 probably doesn't need redundancy as much as the extra capacity anyway. 

Here's the breakdown. Crucial's 512 GB M550 has 512 GB of flash inside. Normally, 93.15% of that would be available as usable capacity, since 512 binary GB * 0.931515 equals 512 decimal GB. But that 4 GB for RAIN has to come from somewhere. So, Crucial takes it out of that ~7% spare area, which is approximately 35 GB. Subtracting 4 GB of room for parity information leaves only 31.06 GB of spare area for the controller's housekeeping algorithms. Apparently, this won't be an issue, particularly given the desktop and mobile environments that the M550 is meant to serve. Of course, we have specific tests to validate such claims...

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  • ikyung
    Heard rumors of Samsung planning to market the 850 with aggressive pricing this year. Would like to see Crucial and Samsung duke it out in pricing.
  • _potts_
    I just splashed $250 (delivered to Oz) on a M500 480GB mSATA, eh, can't complain.
  • cryan
    Heard rumors of Samsung planning to market the 850 with aggressive pricing this year. Would like to see Crucial and Samsung duke it out in pricing.
    They already have IMHO. The Samsung 840 EVO is significantly cheaper than it was at launch. It and the M500 have seemed to move in lockstep. Along the way, we've seen other manufacturers follow suit. Even Intel's 530 series, which has been on the more expensive side of mainstream products has been seen for just $140 for the 240 GB version here in the State.Regards,Christopher Ryan
  • venk90
    INSANELY GOOD DEAL ON AMAZON ! The 512 GB SSD is listed at 169$ incorrectly ! Grab them before they change it. I ordered 20 myself ! Will e-bay all of it or feel bad and return it to Amazon !
  • cryan
    I just splashed $250 (delivered to Oz) on a M500 480GB mSATA, eh, can't complain.
    I hope Crucial continues to sell the M500 right where it is. The deals are just too good, and it'd be truly sad were Crucial/Micron to up the price on us.And they're not slow. I know it seems like they're sub par compared to some of the last few drives we've tested, but the reality is most users are never going to notice the speeds between different SSD models. The only exception is jumping from an older SATA II drive to a modern SATA III SSD. Even then, you'd need solid hardware in the system.Regards,Christopher Ryan
  • Ankursh287
    M500 available at $240 (amazon)..damn good drive for the price, performance difference between M500 , M550 & 840/840 pro won't visible to normal user.
  • Nada190
    When I look at SSD's I want price to performance because I won't even notice a difference.
  • Drejeck
    Specifically for gaming which would be the best? All sort of tricks are allowed, from tweaks to samsung's magician (ram caching).
  • RedJaron
    Of course, we're in the throes of post-launch pricing. In a few weeks, it's possible that the gap between M500 and M500 will narrow.
    Typo on the last page. One of those should be 550.

    Happy to see Crucial with this update. I'm with a lot of people, you don't see a difference in SSD performance outside benchmarks. Give me something reasonably fast with great durability and I'm sold. With all this talk of the maturing of 20nm manufacturing, I'd love to see an M500 V2 with less overprovisioning.
  • gizmoguru
    Hay Tom's the chart for Sequential Reads Benchmark is labled "Random Writes", please correct
  • mapesdhs
    I notice the PCMark Vantage graph's x-axis does not start at zero. This
    is very bad practice, please don't do it. The visual result is totally misleading.
    It makes the results look more differentiated than they really are.

  • game junky
    I have had nothing but good experiences with Crucials M4s so this could be an exciting development depending on how they compete with Samsung. Keep 'em coming, guys
  • snakyjake
    In terms of reliability and maintaining data integrity, how does this compare to SanDisk X210?
  • f s
    M550 price doesn't match the performance unfortunately, $60 less would have made the difference.
  • cryan
    Anonymous said:
    In terms of reliability and maintaining data integrity, how does this compare to SanDisk X210?

    Most data integrity protocols for client/consumer SSDs are centered around maintaining data at rest. That is, once data is written to the flash, you want to minimize and counteract operations which can skew existing data. Things like Read Disturb Management fit this category, where reading one cell can affect the voltages of adjacent cells.

    That said, both drives have three year warranties. Both are made by fabbed SSD manufacturers, both have stakes in NAND foundries. Both use Marvell controllers and custom firmware/PCB packages. When SanDisk updates the X210 with the newer Marvell 9189, it's probably going to be awesome. The X210 is undoubtedly the most underrated drive in circulation. If you can get a good deal on one, it's probably the drive for desktop applications, assuming you want something that's been through its paces. The M550 is too early into its launch to know much about it yet, at least over more than a couple weeks.


    Christopher Ryan
  • frank5868
    Hi, Christopher
    Thanks for the nice review. I have some questions and wondering if you could offer some answers for them:
    Is the drive using AES encryption? 128 bit or 256 bit? How about the "Block cipher mode of action"? Is it ECB? CBC or XTS?
    Please dig as much as possible. I think the readers would be happy to be aware of the mode of action. As well known, the ECB isn't secure but the CBC or XTS is far better.