On Fri, Nov 21, 2008 at 7:28 PM, William L. Maltby <CentOS4Bill at triad.rr.com> wrote: > > On Fri, 2008-11-21 at 18:38 +0200, Rudi Ahlers wrote: >> <snip> > >> I'm sitting with a very expensive paper weight right now, and I don't >> know what todo. The same websites are running very well on a machine >> with a Gigabyte G31MX-S motherboard + 4GB DDRII 800 RAM + C2D 6750 >> CPU. This is what baffles me, how can the same load on a slower >> machine work fine, but on the faster one not? > > Having watched all this thread, I note that certain things are not > mentioned. Assuming that you followed all the previous suggestions, I'll > add my own that is based on practical experience some years back, and > one recent experience. > > Like you, I always built my own. Since you have no way to check the PS, > try removing all components you can and see if that helps. _Usually_ a > weak PS will show symptoms on boot, since all things are spinning up > asnd doing max current draw, but sometimes not. Some BIOS have settings > that allow or automatically "spin up" in a stepped sequence. This would > not stress the PS as much. Keep in mind that PS's have different > amperage draw capabilities for different rails. A seemingly "sufficient" > PS in terms of wattage may be weak on one or more of the rails. Specs > for the mobo and PS might indicate a problem. I also thought the problems was related to the power supply, but I don't have a spare one of these at the moment. I did, however, swap-out the PSU with a standard 350W PSU, and the sympoms were the same, so it's not PSU related in this case. This also reminds me that I should get a spare PSU ASAP :) > > Have you checked the voltage settings in the BIOS for the CPU and > memory? Many/most these days automatically detect, but... I normally leave those on automatic, since I don't like running components outside suppliers specs. > > Check the spec sheets for the CPU and memory sticks. > > I recently upgraded a mobo memory and it would not boot or run reliably. > The spec for the memory was not available and I left the settings as > with the previous memory. Not wanting to fry the sticks and possibly > void the warranty, I picked up the whole thing an carried it back to my > local supplier. I explained the symptoms and told him I suspected memory > voltage but didn't want to try/fry the sticks and risk the warranty. > > Hmmm... he said. Well, long story short, he eventually kicked up the > voltage (I guess the "auto" in the BIOS was flaky or something) and all > worked. Required +.2 volts. Most memory sticks can be run at slightly > higher (+.1, +.2) volts without harm. Larger memory may require a slight > increase in voltage. I guess the "automatic" settings can't always be > trusted. > > Running about 6 months now, NPs. > > Another thing about pulling all components you can: if there is some > kind of IRQ conflict, this can (used to?) cause slowdowns. Maybe that > will be shown there. But that should also leave some traces in > the /var/log/messages or dmesg log. There no add-in cards, nor a CD-ROM / DVD-ROM, only the on-board devices & the HDD's. Taking the HDD's out doesn't help much, since the problems only occur when there's a bit of load on the system. > > Let's presume that the "obvious" problem is not the problem. What if it > is not hardware directly? > > Examine your /var/log/dmesg carefully for any "suspect" messages. I've > also found that occasionally drivers selected by the system may not be > exactly correct. Check the specs for mobo and add-in cards and see if it > looks like the best drivers for the chip sets are loaded (lsmod and > modinfo help here). /var/log/messages didn't show anything related to the problem, at all. > > Grab any old performance/diagnostics software (maybe some on this list > have current knowledge - I don't) and run it. Compare to published data > for same or similar systems. > > Enable sar on the system, run the reports and see where the slowdowns > are. > > I haven't used multi-core yet, but I would first check to see if all the > cores are being effectively used. Maybe top will help here? Not sure. > > BIOS: some have oddball (not really, but legacy issues abound) settings > that may limit amount of memory seen/used? Keep an eye out for those. > Memory timings may not be properly detected and set. Check the specs for > the memory and see if the BIOS has them properly set. BTW, _some_ memory > and mobo combos will allow faster settings, but be careful. I haven't > dinked with them for a long time, so I can't make any Q & A suggestions. > > Have you upgraded to the latest BIOS on the system? Most retail mobos > come with an early BIOS version that has... "issues". Check the > manufacturers web site and see if there is a later BIOS. No, I don't like BIOS upgrades unless absolutely necessary. > > OTHER: Of course, you have manually "re-seated" all connections, yes? A > slightly loose cable, add-in card or memory not fully seated can do > things such as you describe. Other than RAM, the only other cables to reseat are the power cables & SATA cables :) > > Visually inspect cables for "micro-fractures". Better, if you have > access to meters, check for excessive resistance or opens. If not, try > changing out cables. You might want to look in this area only if SAR > reports show slow disk activity. Also hdparm might give some > information. Maybe some settings there would help too. > > That's all I can think of ATM. I hope something of use here. > > -- > Bill > > _______________________________________________ But, I did make an interesting discovery, when I tried to install a fesh copy of CentOS on a new HDD. The installation itself didn't succeed. Everytime I had to choose an option, on any screen, during installation, all the fans would spin up to it's max speed & everything would be really slow. It's almost like trying to install CentOS on a 486 computer. Yet, none of the heatsinks felt warm, even as warm as the hard drives. So, I came to the conclusion that the motherboard is faulty. Right now, I only have a spare Gigabyte motherboard handy, which when I used it didn't give me any problems whatsoever. I'm using the same 1U chassis with limited air flow and small fans, and it runs as smooth as it should. I have since swapped out the motherboard with the supplier, and the new motherboard seems to run very well. Installation took about 20minutes to complete. Thanx for all your help :) -- Kind Regards Rudi Ahlers