Recently I had a problem with one of the servers I manage. It is a Debian stable machine running Linux kernel virtual machine (KVM). One of the virtual machines inside the system kept having memory errors and was crashing. More here
Along with a bunch of stack traces for each of the programs. Interneting this led me to believe that there was a problem with the ram on the system. So I marched down to the colo, put a memtest86 ISO in the system and let it sit. After about an hour with no memory tests, I concluded it probably wasn’t a hardware problem.