Date: Mon, 06 Jun 2011 17:27:20 +0100 From: "Dave" <dave@g8kbv.demon.co.uk> To: freebsd-questions@freebsd.org Subject: Re: Strange system lockups - kernel saying disk error Message-ID: <4DECFFE8.6627.A0067AF@dave.g8kbv.demon.co.uk> In-Reply-To: <isgq3c$i77$1@dough.gmane.org> References: <4DE8CF13.1040304@gmail.com>, <isgq3c$i77$1@dough.gmane.org>
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On 5 Jun 2011 at 16:55, Michael Powell wrote: > perryh@pluto.rain.com wrote: > [snip] > > > > Power supplies do fail occasionally, and not always in obvious > > ways such as failing to turn on at all. The output voltages may be > > a little too high or too low, or they may be correct but with > > excessive ripple or electrical noise; or the supply may be just fine > > until a disk draws a current spike to move the arm rapidly. > > I've seen a fair number or power supplies degrade somewhere around the > 5 year mark. Simple voltage checks with a VOM and its accuracy will > usually still show the voltages as being correct. To see the ripple > you'll need an oscilloscope. Excessive ripple can make a PC appear to > have all kinds of intermittent hardware failures with little or no > rhyme or reason. A degraded power supply will show large variations in > ripple based on load. The largest load from hard drives is when they > are first spinning up. Servers are commonly configured with the > ability to spin up drives one at a time with a short delay in between. > You won't usually find this on a desktop. > > Generally, this situation will develop more often on an old machine > that had a 'barely enough' capacity power supply when new. Add 3 more > hard drives, bigger video, etc and it was still just inside the > envelope until enough time went by and the power supply got old. Since > the most amps pulled by the hard drives occurs on power up you will > see the ripple on a 'scope look really ugly while this happens. The > unseen danger here is that bits on the drive(s) can get scrambled > until things settle down. You will know this happens when stuff goes > wrong and fsck is needed to get the file system clean, and after > cleaning and working again will do the same thing again at some future > reboot. > > Easiest way to look at this without a 'scope is to simply substitute a > known good PSU of sufficient rating from a machine with no troubles. > If all the random nonsense suddenly stops, you'll know. This is > easiest for folks these days as those without an analog electronics > background are unlikely to have an oscilloscope laying around. > > > It might be worth checking the fan mounted on the CPU heatsink if > > there is one, and the fan in the power supply (which ventilates the > > case as well as the power supply itself). > > Aside from the fans themselves, dust buildup plugs heat sinks > eventually drastically reducing their ability to get rid of heat. When > you get to this stage blowing them out with canned air can work > wonders. My 2 servers at home sit on the floor and need this about > once a year. > > -Mike > Hi.. I've recently replaced all the 3.3V decoupling caps on a 7 year old Compaq mobo, that was showing all sorts of odd behaviour, more (at first glance) related to the video card. It wasn't expensive, but was time consuming even for me as a skilled electronics tech, with more years of soldering iron time than I care to admit, it took me a good couple of hours! These things aren't made to be easily repaired, but it can be done. In fact, for some common mobo's you can buy complete re-cap kits with all the right parts. Same for all sorts of other consumer electronics. (DVD players, Games consoles, DTV and other set-top boxes etc.) As a result, that box now runs sweet as a nut. Passing all diags with flying colours, even when hot. Any caps that have a bulging top, on the mobo or in the PSU, need changing. Idealy for the same value and voltage. But you can go higher (within reason) in value, but don't go too high in voltage rating, as they can deteriorate if they don't have enough volts, and start to fail early again. Re the PSU thing. Don't get fooled into the common lore that bigger is better. You can have too big a PSU that will fail to regulate the auxilary output lines correctly until you add extra load to it's main output. Many PC supplies (sadly not all) do have a note to that effect on the ratings label. For most Switch Mode supplies, they work best loaded to between half and full power on their main output. Much less than 1/4 of their capability, and the auxilary outputs will start to "wander about" a bit, especially if the incoming line is a bit high in voltage. Common symptoms are strange audiable noises from CD drives, or hard drives that struggle to start up, but are OK once working. Yes, also keeping things clean and cool is a good move too. Hope that helps someone. Cheers. Dave B. PS: I don't suppose anyone knows a real good simple blow by blow total newby dialog, as to how to realiably and correctly create and setup Jails on FreeBSD 8.0? All the man pages I've found so far, are way over my head. Good "Reference" material admittedly, but no good as an instructional if you dont already know "How To"... I don't understand ezjail either... Something to do with the faded grey cell and too many years etc...
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