Date: Thu, 1 Nov 2012 16:07:52 -0400 From: Zaphod Beeblebrox <zbeeble@gmail.com> To: Dennis Glatting <freebsd@penx.com> Cc: freebsd-fs@freebsd.org, Ronald Klop <ronald-freebsd8@klop.yi.org> Subject: Re: ZFS RaidZ-2 problems Message-ID: <CACpH0Me5khBL561RkP5v4DspEvn7xcwR9=Su4bzVLAkZ_D9vgw@mail.gmail.com> In-Reply-To: <1351739465.25936.5.camel@btw.pki2.com> References: <508F98F9.3040604@fletchermoorland.co.uk> <1351598684.88435.19.camel@btw.pki2.com> <508FE643.4090107@fletchermoorland.co.uk> <op.wmz1vtrd8527sy@ronaldradial.versatec.local> <5090010A.4050109@fletchermoorland.co.uk> <op.wm1axoqv8527sy@ronaldradial.versatec.local> <CACpH0MeJpSg3ti-QUgT=XwaC0jkEo5JeBAfRGPTFfUE6eLJFJg@mail.gmail.com> <1351739465.25936.5.camel@btw.pki2.com>
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On Wed, Oct 31, 2012 at 11:11 PM, Dennis Glatting <freebsd@penx.com> wrote: > To be clear, I am unsure whether my problem was the power supply or the > wiring -- it could have been a flaky connector in the strand. I simply > replaced it all. > > I had a 1,000W power supply drawing ~400W on the intake. Assuming 80% > efficiency, the power supply should have had plenty of ummpf left. > Regardless, the new power supply was cheap compared to my > frustration. :) Well... to test the power supply, you really need to "scope" the power that the drive uses... likely 12V. Bad wires can also be of effect here, but not everyone has a scope. It's not about the % of available capacity in the case of a bad power supply unit, it's about the quality of the unit itself. What _I_ was talking about was the input to the unit. Roughly, as I understand it, switching power supplies work by "filling" the capacitors that "float" the voltage rails by diverting power from the incoming sine wave to the capacitor when it is above a threshold. A quality supply that is lightly loaded might run several seconds without power before the capacitor drains to the point of shutting off. The "quality" of the power supply comes in removing the waveform from the voltage rail that would otherwise result. Now... my suspicion of the parent's power problems come in the form of the power supply unit's reaction to brown-outs that are not severe enough to trigger the inexpensive (off-line) UPS. If the result of the brown-out is a dip in the voltage on the 12V rail while (coincidentally) the drive is writing to the disk... this is where the drive starts to loose sectors fairly rapidly. To put it more graphically: good power + cheap power supply unit == mostly working computer. bad power + cheap power supply unit == dead disks. good power supply units are generally a good idea.
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