With raid10,f2 you can almost double the sequential read performance of your raid, while other performance numbers are about the same.

Using all of the 4 drives you can 4-double your read performance, and something like double other read performance measures, compared to your setup, while writing will be about the same. I would also recommend using a bigger chunk size, say 256 KiB.

Your point 3 would then be:

I would also recommend using raid for boot and swap, and using all of the 4 drives would actually let you run if even 3 disks crashed, plus you get the added performance of all of the drives. /boot need to be on a standard raid10, as grub and lilo only can boot raid partitions that looks as a standalone partition.

Say for /boot:

mdadm -C /dev/md1 -c 256 -n 4 -l 10 -p n4 /dev/sd[abcd]1

And for swap:

mdadm -C /dev/md3 -c 256 -n 4 -l 10 -p f4 /dev/sd[abcd]3

For /home I would not waiste all the space on having 4 copies, so:

mdadm -C /dev/md4 -c 256 -n 4 -l 10 -p f2 /dev/sd[abcd]4

You may even consider running RAID5 on /home, to get more space.

There is more on the setup at  http://linux-raid.osdl.org/index.php/Preventing_against_a_failing_disk

Compared to your setup, this would give you:

1. Survival of 3 disks crashing - your setup would not survive a dish crash where your /boot was placed, and your setup will stop if any of your swap partitions were damaged.

2. Almost 4 times the sequential read performance, and double random read performance for your basic /root and swap partitions.