I was thinking of getting 2 SATA disks (80GB each) and set them up as RAID 0 fo r Windows XP and Linux..

However, I found out that my VIA vt8237 based mobo is not a real RAID hardware solution, so I stopped thinking of it.

I have currently a 120GB WD JB ATA disk and I will buy a SATA (120GB).. If I create a softraid partition (RAID 0) on those disks, will I see a noticeable speed increase or I will lose my cpu cycles for nothing?

I don't care about windoze, but I need the speed for my everyday linux use...

The rule-of-thumb for setting up a high performance Raid is that the drives should be identical, which means a lot more than just having the same model number, and that they should be on the same data channel (PATA vs. SATA vs. SCSI). That can be relaxed a bit if you just want to set up a Raid1, which your proposed configuration would probably do nicely.

Just for grins, I once tried setting up Linux Software Raid0 and Raid5 on a system with 2 SATA drives (WD800JD) and 1 PATA drive (WD800JB). The read speeds (i.e., hdparm -t) were no better than the PATA drive alone.

In contrast, the read rate (i.e., hdparm -t) for a linux software Raid0 set up on 2 PATA drives (2xWD800JB or 2xWD2000JB) through a Promise Ultra100 TX2 controller were just barely short of twice the read rates for the individual drives (105MB/s for Raid0 vs. 55MB/s for single drives). Similar results were seen for a linux software Raid0 using 2 SATA drives (2xWD800JD) and a Promise FastTrak S150 TX2plus controller.

Interestingly, although the Western Digital SATA drives usually give slightly faster read rates than the identical PATA WD drives, the SATA drives are usually only 5-10% faster than the PATA drives.

I will be using only a portion from the two drives..

I am thinking the following:

/dev/hda (my SATA is recognized as hda)
/boot/ ext2 : 200MB (just in case - hey I'll have 240GB
swap1 : 1GB
/dev/md0 reiserfs: 30GB raid of / (RAID 0 stripping)
/dev/md1 reiserfs: 20GB raid of /home (RAID 1 mirroring)
the rest I will see

/dev/hde (1st PATA device)
swap2 : 1GB
/dev/md0 reiserfs: 30GB raid of / (RAID 0 stripping)
/dev/md1 reiserfs: 20GB raid of /home (RAID 1 mirroring)
the rest I'll see and decide....

Will this hurt my computer's perfomance? (Athlon XP 2700+, 512MB RAM)