Linux: using md to get RAID1

I wanted to give few extra years to our old server (which was replaced with new SMP Celeron box), so I decided to turn it into WiFi AP. However, it came with two disks, one of 4.3Gb (QUANTUM FIREBALL CR4.3A) and one with 6.4Gb (SAMSUNG SV0644A). Since those disks used to be ftp site, I don't trust them much, and hence I decided to put software RAID 1 on them.

For this project I used:

1. pentium server (SMP with P5/200)
Debian Woody (3.0r0 and latest unstable)
LILO 22.2
linux kernel 2.4.18
Procedure involves many steps, and some of them must be performed in this order. However, that is not the only possible order. Helpful hints are marked specially.

Speed comparison

Read a 50Mb file from different partitions using
time dd if=/50Mb of=/dev/null
partitiondescriptiontime (real)time with dma
/dev/md1 mirror raid1 from /dev/hda1 (Samsung 6.4Gb) and /dev/hdc1 (Qunatum 4.3Gb) 8.930s 3.825s
/dev/hda3 non-mirror on rest of Samsung 6.4Gb (also used for mirror) 8.905s 4.516s
/dev/hdf1 non-mirror on IBM-DJNA-371350 13Gb (on separate CMD649 controller) 13.450s 4.558s
So, use DMA modes with hard drives, especially larger ones.