Is there any performance advantages when the hard disk is the master or it doesn't matter?
You will have to set the CDROM as the slave.
This thread has exactly this question. One of the post asserts that setting the CDROM as master will cause the hard drive to operate slowly.
Though this post from 2004 states:
Though things could have moved on since then,
If the HD is set to Master or Slave, then the CD drive must be the opposite. If the HD is set to CS (Cable Select) then the CD drive must be set to CS as well (this assumes you have a somewhat modern IDE cable, usually with different colored connectors for each drive).
If your computer is using both drives at the same time they'll each get half of the IDE cable's bandwidth. So there may be a performance hit. Having one or the other set to master should not impact the other's performance. Also, if a drive is set to slave there must be a master on the cable as well (for most drives).