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We recently have a computer with 3 out of 5 HD going bad (excessive bad sectors) within 1 week. This got me to start thinking that maybe it's the power supply. What are some warning signs / tricks to tell when the power supply is about to go? before it completely stop working.

I read on another thread on SF about power supply tester. It looks helpful if the PSU has a faulty rail, but will those catch intermittent errors that might happen before a supply goes bad?

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up vote 2 down vote accepted

What you need to catch are voltage drops and spikes, some less than 100ms long, and that over a period of serveral hours. That power supply tester won't catch those, and I don't know of any device that does.

You can hook up a sensitive voltmeter, if you can see the voltage vary there's definitely a problem, but it won't catch all problems.

There is also another possibility: you could have drives all from the same bad batch.

In this case I would take no chances. Replace the PSU and start transferring data to fresh drives.

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Doesn't PSU requires a load in order to show correct voltage? – fseto Sep 8 '10 at 10:29
@festo: yes. I didn't mention this should be done under load on a running system – Joris Sep 8 '10 at 18:24

I hook my multimeter up to it (5 and 12V) it then records surges and brown outs if any.

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Just to start, every time I have personally seen a a series of HDDs fail in rapid succession in one machine it has turned out to be caused by a bad power supply. So, I'd say don't stuff around: replace the PSU and all the HDDs (including the ones that are currently "fine") immediately.

One exception to this rule would be if all the HDDs are new(-ish) - in which case it could be a bad batch - but I'd still go ahead and replace the PSU (and of course HDDs) anyway.

Re the warning signs of a bad PSU, in my experience:

  • failing component(s), often multiple components in a short space of time (like your HDDs)
  • instability (most noticable if the system has been rock solid historically) - apps crashing, strange errors, hard-freezes, BSODs, etc.
  • strange smells or sounds coming from the PSU
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If it's a "proper" server, monitor it! Most real servers have a Lights Out Management interface which is basically a small "computer"(TM) in your server, capable of monitoring sensors, voltages, power supplies, physical intrusion detection etc.

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smell the exhaust coming out of the power supply. If it smells like burnt coffee, one or more of the capacitors has blown. Make sure the fan on the power supply is still running. If it is reasonably old, replacing it with a new one is relatively cheap insurance.

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Or a slightly acidic metal smell, also a dead giveaway. But there are other problems besides bad caps that can cause problems. – Joris Sep 8 '10 at 6:27
If you can smell magic smoke 1 2 then it's time to retire something. – Iain Sep 8 '10 at 7:47
You're lucky. I usually don't get to smell the magic smoke until it's preceeded by a loud BANG and the noise in the server farm getting a tad bit quieter, followed by the eerie sensation of millions of electrons crying out and being suddenly silenced...then the phone rings from users wondering why they can't get to XYZ system. Oh, the wonderful Mondays... – Bart Silverstrim Sep 8 '10 at 12:17

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