Random I/O

If you have a random I/O environment, such as an environment used for databases and general-purpose file servers, you want all disk spindles to be approximately 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 load is truly random and evenly dispersed across the entire range of the table space, then each of the four spindles will tend to be equally busy, which will generally improve 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 will not improve performance. You must create a new volume with the ideal parameters to optimize performance.

The interlace size of the stripe doesn't matter because you just want to spread the data across all the disks. Any interlace value greater than the typical I/O request will do.