Friday, March 8, 2013

Some interesting SSD tidbits

Now that SSDs are poised to completely replace spinning rust, I've been trying to learn more about them. As always, I'm behind the curve, and rushing to catch up.

A few fun pointers I happened upon recently:

  • Understanding the Robustness of SSDs under Power Fault
    Applying our testing framework, we test fifteen commodity SSDs from five different vendors using more than three thousand fault injection cycles in total. Our experimental results reveal that thirteen out of the fifteen tested SSD devices exhibit surprising failure behaviors under power faults, including bit corruption, shorn writes, unserializable writes, metadata corruption, and total device failure.
  • Redis with an SSD swap -- not what you want (see the original article at Redis with an SSD swap -- not what you want)
    I already guessed that the SSD swap setup would perform in a bad way, but I was not expecting it was *so bad*.

    The point is simply to show how SSDs can't be considered, currently, as a bit slower version of memory. Their performance characteristics are a lot more about, simply, "faster disks".

    Now those new disks are fast enough that if you design a database specifically to use SSDs, you can get interesting performances, compared to old disks. However the idea to use the disk as something you can use to allocate memory will not work well, and complex data structures requiring many random access writes, will not work either.

  • The Full Intel SSD 525 Review: 30GB, 60GB, 120GB, 180GB & 240GB Tested
    This is really a big problem with SandForce drives if you're going to store lots of incompressible data (such as MP3s, H.264 videos and other highly compressed formats) because sequential speeds may suffer even more in the long run. As an OS drive the SSD 525 will do just fine since it won't be full of incompressible data, but I would recommend buying something non-SandForce if the main use will be storage of incompressible data.

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