The default value is 128, which is acceptable for small systems. Larger systems could use higher values to increase mirror resynchronization speed.
128 to 2048
Blocks (512 bytes)
If you use Solaris Volume Manager RAID 1 volumes (mirrors) and you want to increase the speed of mirror resynchronizations. Assuming that you have adequate memory for overall system performance, you can increase this value without causing other performance problems.
If you need to increase the speed of mirror resynchronizations, increase the value of this parameter incrementally (using 128-block increments) until performance is satisfactory. On fairly large or relatively new systems, a value of 2048 seems to be optimal. High values on older systems might hang the system.