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OT; Power faults and SSD's

Discussion in 'Electronic Design' started by Martin Riddle, Apr 28, 2013.

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  1. A while back there was a discussion of power failures and the effects on
    Hard disks.
    Well, not really discussion but a 'Yes, it does happen' vs. a 'No, it
    doesn't happen' post.

    Anyway, I found this article that points out SSD's are more susceptible
    to power faults.
    <http://www.zdnet.com/how-ssd-power-faults-scramble-your-data-7000011979/>

    And here is the link to the paper.
    <https://www.usenix.org/system/files/conference/fast13/fast13-final80.pdf>

    You need a few extra fingers and toes to count the faults on SSD's Vs.
    the few faults on a rotational disk.

    Cheers
     
  2. Thanks for that. Another good reason to have a UPS.
     
  3. miso

    miso Guest

    Thanks for that. Another good reason to have a UPS.
    You obviously didn't read the paper. They created a fake power failure
    by gating power through a kludge protoboard circuit. They did not turn
    off the AC to the power supply. Who knows how much ringing their was on
    the power supply pin due to wiring inductance and di/dt. A computer
    power supply has some hold time. Their test is quite bogus.

    To elaborate, these wankers left the data bus connected to the SSD while
    they gated the supply voltage. This is a prescription for inducing latch-up.

    Direct gating of the power to a device via a fet is just bad. Yes it is
    done, and yes most manufacturers will at least lab test their parts to
    insure reasonable behavior under such circumstances, but such
    shenanigans are not in the test flow. Chips provide power down
    pins/modes. Use them.

    While I'm at it, most home UPS are cheesy square wave (OK, "modified")
    inverters that hopefully switch on in time. The data centers use double
    conversion UPSs.
     
  4. miso

    miso Guest

    Good SSD models have built-in power loss protection:
    I have two 320 series SSDs. So far so good. Even the next generation
    Intel SSD has a 5 year warranty.
     
  5. Jasen Betts

    Jasen Betts Guest

    are you suggesting that maybe software could have corrected some of
    the hardware failures, one problem it could also compound them and it
    makes comparisons harder.
    true, are you suggesting they did?
    that depends what it'se being used for OLTP, DVR, and video editing
    all write in with a high frequency,

    particularly if they have plenty of RAM.
    these are real numbers from an OLTP database server.

    34 734 222 256 sectors written vs 8 381 621 185 read

    Roughtly 4:1 in favour of writes.
    They probably wanted to avoid the fervid attention of lawyers.
     
  6. Jasen Betts

    Jasen Betts Guest

    yeah, I saw a demo on you-tube (possibly "Shouting in the Datacenter")
    and was able to replicate those results on a smaller scale in the office

    on linux
    ddrescue /dev/sda /dev/null --force

    then shout at the drive and watch the data rate dip.
     
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