Re: Soft-Updates for Linux ?

From: Albert D. Cahalan (acahalan@cs.uml.edu)
Date: Mon Oct 02 2000 - 01:03:07 EDT

  • Next message: Robert B. Easter: "Re: ide-scsi problems with plextor IDE drive"

    Robert Redelmeier writes:
    > Daniel Phillips wrote in part:

    >> One thing to keep in mind in all of this is: nobody is testing the
    >> reliability of their journalling or any other kind of filesystem just by
    >> running it. To test these things you have to crash/interrupt the system
    >> *a lot*. Otherwise, you are just fooling yourself and everybody else.
    >> How many crashes does it take to find that one little window of
    >> vulnerability that comes up every 10,000 crashes normally but suddenly
    >> starts coming up every time just because your customer uses their system
    >> a different way? You're doing the right thing by crash-testing it, now
    >> instead of doing it 5 times do it 1,000 times. Here's one of my
    >> favorite tests: unzip a kernel source tree and wait until the disk light
    >> goes out. A second or so after it comes on again (kflushd) hit the
    >> reset button.
    >
    > Good idea. I certainly believe in stressing hardware (see .sig),
    > but I'm not sure this test is rigorous enough. The problem is
    > the reset button is only connected to the CPU and the hard disk
    > will probably continue to write out sectors from it's hw buffer.
    > OTOH, I don't like the idea of pulling the plug too often. It's
    > very hard on the hardware. I'd expect a mechanical disk failure
    > before 10,000 cycles.

    The nice way to develop this code is with a block device that
    discards all writes after a timer goes off.
    -
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