For disk I/O see:
http://serverfault.com/questions/126...sh-dirty-pages

One more thing to try is try a different filesystem and I/O scheduler.

http://blog.nexcess.net/2010/11/07/c...-io-scheduler/

I recommend JFS and deadline I/O scheduler, but you can try other combinations and see if it helps.

I have been testing new performance settings in the 3.2 kernel, and I strongly recommend using this kernel PLUS turn on zcache (not zram, but can be used with zram if you want). I've found zram to mostly be useless, but zcache does what it says it does and works well so far. The 3.2 kernel has lots of performance improvements that may solve this issue. It solved all my performance issues. I also enabled huge pages, but this may not be needed.

I have also found some of these settings to also improve performance:
http://kb.lsi.com/KnowledgebaseArticle11050.aspx

Hmm, that's very interesting. I am still planning on installing from scratch with 64 bit, but I think ArchLinux is only on 3.1.7 kernel. But anyhow it's a rolling release so as soon as 3.2 is ready. I just haven't yet had time to rebuild my machine--work keeps getting in the way.

Thank you.

I am responding to an old thread that I started, but I want to finish the story.

I bought a new disk and installed it and then installed Arch 64 bit there. While using my 32 bit install later, I mounted the new disk and opened it in Thunar and heard the crazy scraping noise. No question that this is a software issue NOT a hardware issue.

The new install works beautifully! I am using Openbox now which I may end up liking even better than Xfce. I unzipped a 20 MB archive and no sound. I ran now an import of a 330 MB SQL dump. It also ran fine and the disk was completely silent. As a matter of fact, thus far everything is quiet. Finally.

I now see:

I.E. I now have my full 4G (total before was 3271).

Seems whatever it was, it is now fixed.

Thank you to everyone who helped.