Brian May <brian@microcomaustralia.com.au> writes:
1. If I boot anything later then 3.12 kernel, I don't get any display. As in the monitors display black. [...] Computer seems to be up and running, and responsive to crl+alt+del despite not having a display.
So SSH into it and investigate. You say you're running wheezy with 3.12. Are you using the bpo kernels? Those are currently at 3.14.
2. There seems to be some weird performance problem. e.g. save a 2 kilobyte file in vim, and the computer can completely freeze (all other windows, including xterms, stop responding to user input) for, say 30 seconds, while it is writing that file. Chromium takes ages to load with several tabs, and pages can fail to start properly while it is doing so.
I can't account for this unless your storage is on eMMC or similar. Have you looked for processes in D state & run iostat?
This is moving disk + RAID1 + LVM + ext4.
OK so not eMMC. Are the blocks aligned? Shouldn't really matter for RAID1 or spinning rust, tho. Ty T'so had a blog post a while back explaining how to laboriously align everything, if you care enough to try that (I wouldn't bother unless you were reinstalling anyway).
I am currently working on a new theory that the performance problems only occur when the computer is cold and first turned on. I think I have seen evidence to disprove this, but guess I should run bonnie++ as soon as I turn the computer on, just to be sure.
And in break or single mode, so no other shit is running.