I'm glad to see you've got this sorted Nick, I just had a couple of
comments:
a) RAID-5 + hot swap spare on four disks. So that's Data + Data +
Parity + Spare - a 50% usage rate. RAID-1 will give you that and much
better write performance. There is a higher chance of failure if you
lose two disks though.
b) I don't really think LVM will add that much overhead - yes it's a
mapping but compared to disk performance. In fact, the only thing I
could see is about lvm1 (not lvm2) - I can't actually see any drop in
performance!
http://www.linuxkp.org/en/content.php?&content/server/lvm1.html#perf
http://arxiv.org/pdf/cs.PF/0508063.pdf
What I do now is:
Create two partitions on each disk:
/dev/sda1 (100MB)
/dev/sda2 (most of the disk)
SW-RAID /dev/sd[ab]1, use as /boot
SW-RAID /dev/sd[ab]2, use as PV for LVM
Create /, /home, /var, /tmp (etc) on LVM
This is all supported nice and easily using the Debian installer -
_unless_ you preseed (automated install). I've had to write my own
partitioner to do this :( Which would be simple barring the number of
places you need to wait until devices actually appear (e.g. when you
create a partition, it can take a few seconds for /dev/sda2 to appear
even though parted has returned).
Adrian
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