08. Is it ok to have 2 IDE drives on one cable?
Yes it is, but bear in mind that you are sharing the bandwidth of the cable & controller equally. Thus you may loose performance, especially when copying from one drive to the other.
If you have two modern (fast) IDE drives you may see better performance with each drive on a dedicated IDE channel. Care must also be exercised when dealing with Hard drives and Optical drives. Ideally for maximum performance you would want each hard drive to have its own cable, with any optical drives sharing a seperate cable. This can be a complex balancing issue, so read the following 2 links for more details.
# Master/Slave Channel Sharing: By its very nature, each IDE/ATA channel can only deal with one request, to one device, at a time. You cannot even begin a second request, even to a different drive, until the first request is completed. This means that if you put two devices on the same channel, they must share it. In practical terms, this means that any time one device is in use, the other must remain silent. In contrast, two disks on two different IDE/ATA channels can process requests simultaneously on most motherboards. The bottom line is that the best way to configure multiple devices is to make each of them a single drive on its own channel, if this is possible. (This restriction is one major disadvantage of IDE compared to SCSI). An add-in controller like the Promise "Ultra" series is a cheap way of adding extra IDE/ATA channels to a modern PC.
http://www.pcguide.com/ref/hdd/if/ide/confPerformance-c.html
Secondary IDE channel - DVD master & CD-RW slave.
Onboard RAID channel 1 - backup HDD.