I've got a hard lockup in the ide subsystem, probably
due to some irq spew or something like that.
I've just bought a brand new Maxtor 320GB disk driver for the insane price of $70 US to replace another failing drive. It works well under light load;
I was able to copy about 60GB to it. However, under heavy load, such as reconstruction of an MD RAID-1 array, it'll lock up the kernel. Which means
that my system won't boot :-(
I'm running 2.6.21.1, although the problem seems to occur in 2.6.19 and 2.6.18 too; its been there a while; I vageuly
remember similar problems in 2.6.5 or 2.6.10.
I can get the system to boot by sneaking in an "hdparm -d0 /dev/hdc" early in the boot process, to turn off
the use of DMA, but it seems that PIO is so slow, that it takes forever to get NFS started.