That was how I read your thread title.
My best advice is to have an independent IDE/ATA controller at least for either a dedicated HDD or the DVD burner to use.
Make your IDE channels as broad as possible. One device per controller is best but that may cost too much for PC. S-ATA or SCSI HDDs plus P-ATA ODDs is an ideal configuration I can think of. OCFreak's test machine is a great example. Take care of heat as well. Heat often affects multiple burning.
Onboard P-ATA channel 1: DVD Burner #1 (bootable)
Onboard P-ATA channel 2: DVD Burner #2
Add-on S-ATA card channel 1: HDD #1 (bootable)
Add-on S-ATA card channel 2: HDD #2
DVD 6x speed is about 8.3MB/s which is about 66Mbps.
Most existing notebook hard disk drives, factory-installed, cannot sustain DVD 8x speed. I tried GbE networks but the main bottleneck was with the hard drives.
1GB DDR memory modules have become reasonably inexpensive. Having 4GB to 8GB memory in one system is no more a luxury. 4.7GB RAM-based drive for compressed files, temporary internet files, and even DVD-Video files waiting to be copied onto recordable DVD media. 80MB/s and 160MB/s SCSI controllers and hard drives have also become cheap. A RAID 0 drive with 160MB/s SCSI can also do 12x DVD writing better than common P-ATA systems.