--On Monday, September 26, 2011 12:11:47 PM -0700 Benjamin Smith <lists at benjamindsmith.com> wrote: > I'm trying to figure out why 2 machines have a "hard I/O lock" on the HDD > when running EL6. I _won't_ chime in with a "check your <whatever>". Instead here's a potentially useless datapoint: I have an older but still usuable 32 bit 686 class machine that was formerly a production machine running Fedora Core 6. Its services were migrated off a while back and I decided I'd use it as a test of CentOS 6. For this test I needed a few disks in RAID6 and the motherboard only had two SATA ports so I added a multiport PCI SATA card (a model that has served me well in the past). Short version: Although the install went fine, trying to run CentOS 6 on this with a four disk RAID6 (with the first 200MB of each disk in RAID1 for /boot, the remainder as RAID6 with LVM on top) resulted in an unstable system. After some unpredictable amount of time (anywhere from 15 minutes to days) the system would lock up hard. Unfortunately I don't recall if the error messages were identical to yours, but it seems eerily familiar. I did the usual tricks about swapping out drive controllers, disks, using different combinations of onboard vs addon SATA, memtest86, increased power supply capacity, etc. No dice. I eventually ended up getting new hardware for the task (an HP MicroServer) and so far the new machine seems to be stable enough running CentOS 6 in the RAID1 /boot + RAID6 LVM configuration. I've not had the chance yet to go back and experiment with the old machine under C6. Unfortunately in trying to use C6 on the old machine I wound up with far too many changed variables to figure out where the problem was. Despite that, my gut tells me that it's not a hardware problem. Devin