The important physical performance characteristics of disk hardware are the relative amounts of I/O on each drive, and the concentration of the I/O within a drive to minimize seek time. Based on monitored results, you can then move the location of subdisks to balance I/O activity across the disks.
The logical priorities involve software operations and how they are managed. Based on monitoring, you may choose to change the layout of certain volumes to improve their performance. You might even choose to reduce overall throughput to improve the performance of certain critical volumes. Only you can decide what is important on your system and what trade-offs you need to make.
Best performance is usually achieved by striping and mirroring all volumes across a reasonable number of disks and mirroring between controllers, when possible. This procedure tends to even out the load between all disks, but it can make VxVM more difficult to administer. For large numbers of disks (hundreds or thousands), set up disk groups containing 10 disks, where each group is used to create a striped-mirror volume. This technique provides good performance while easing the task of administration.