In a random I/O environment, such as an environment used for databases and general-purpose file servers, all disks should spend equal amounts of time servicing I/O requests.
For example, assume that you have 40 Gbytes of storage for a database application. If you stripe across four 10 Gbyte disk spindles, and if the I/O is random and evenly dispersed across the volume, then each of the disks will be equally busy, which generally improves performance.
The target for maximum random I/O performance on a disk is 35 percent or lower usage, as reported by the iostat command. Disk use in excess of 65 percent on a typical basis is a problem. Disk use in excess of 90 percent is a significant problem. The solution to having disk use values that are too high is to create a new RAID-0 volume with more disks (spindles).
Simply attaching additional disks to an existing volume cannot improve performance. You must create a new volume with the ideal parameters to optimize performance.
The interlace size of the stripe does not matter because you just want to spread the data across all the disks. Any interlace value greater than the typical I/O request will suffice.