Technically, for the best flow of data your source of data should not even be on the same IDE as your destination drive. And your destination drive is always best as Master. Your source drive can be either master or slave.
I operate using this setup
IDE1 primary master : NEC 3500AG
IDE1 primary slave : Maxtor 120GB HDD
IDE2 secondary master : NEC 3500AG
IDE2 secondary slave : Western Digital 160 GB HDD
IDE3 primary master : dvd reader (WinXP Promise UltraMB IDE controller)
IDE3 primary slave : dvd reader
IDE4: secondary : no drives attached
IDE5: primary master : Western Digital 120GB HDD (boot drive) (Silicon Image RAID controller)
IDE5: secondary : no drives attached.
In theory, my 2nd dvd rom would be best on IDE5 as secondary master. However, at the moment, I lack the necessary IDE cable to do this and besides, things are already conglomerated enough.
But the above setup works better than any other I have tried, and believe me I have tried A LOT of setups. The 2 NEC drives can certainly cope doing simultaneous 12x burns on the fly ... Or burn simultaneously 12x from 2 separate hard drives. With Maxtor 120GB supplying primary master NEC, and WD 160GB suppling secondary master NEC. Which breaks my rules, I know, but works well nevertheless. So, I guess I must be doing something right.