Background Information for Creating RAID-0 Volumes

RAID-0 Volume Requirements

When you are working with RAID-0 volumes, consider the following:

• Use components that are each on different controllers to increase the number of simultaneous reads and writes that can be performed.

• Do not create a stripe from an existing file system or data. Doing so will destroy data. Instead, use a concatenation. (You can create a stripe from existing data, but you must dump and restore the data to the volume.)

• Use disk components of the same size for stripes. Striping components of different sizes results in wasted disk space.

• Set up a stripe's interlace value to better match the I/O requests made by the system or applications.

• Because a stripe or concatenation does not contain replicated data, when such a volume has a component failure, you must replace the component, recreate the stripe or concatenation, and restore data from a backup.

• When you recreate a stripe or concatenation, use a replacement component that has at least the same size as the failed component.

RAID-0 Volume Guidelines

• Concatenation uses less CPU cycles than striping and performs well for small random I/O and for even I/O distribution.

• When possible, distribute the components of a stripe or concatenation across different controllers and busses. Using stripes that are each on different controllers increases the number of simultaneous reads and writes that can be performed.

• If a stripe is defined on a failing controller and another controller is available on the system, you can “move” the stripe to the new controller by moving the disks to the controller and redefining the stripe.

• Number of stripes: Another way of looking at striping is to first determine the performance requirements. For example, you might need 10.4 Mbytes/sec performance for a selected application, and each disk might deliver approximately 4 Mbyte/sec. Based on this formula, then determine how many disk spindles you need to stripe across:

  10.4 Mbyte/sec / 4 Mbyte/sec = 2.6

  Therefore, you need three disks capable of performing I/O operations in parallel.