IT8212 Raid card speed


Today I bought a new HDD (WD PATA 320GB AAJB). I already have two Samsung drives connected to the mobo IDE controller, the secondary is with a NEC writer.
So i hooked the WD drive to the Inno RAID card IT8212. It work fine, but it is much slower than my other two Samsung drives. What can be the problem?

Can I use this Raid card to connect my DVD writer and than I could put the WD drive to IDE2 or what should I do?

Samsung 1 to Samsung 2 copy (IDE 1 master, slave): 37000 kbytes/s average, AVI file 350MB.

Samsung 2 to WD (IDE 1 slave, IT8212RAID): 20000 kbytes/s average, same file.

Is this the maximum speed for this RAID card?

Please help me out on this.