Compaq 3200 manual Software-Based Drive Mirroring, 28Understanding Drive Arrays

E-28Understanding Drive Arrays

Software-Based Drive Mirroring

Some operating systems support software-based drive mirroring as a fault- tolerance feature. Software drive mirroring resembles hardware-based drive mirroring (RAID 1), except that the operating system mirrors logical drives instead of physical drives.

A pitfall of software-based drive mirroring is that the operating system believes each logical drive is a separate physical drive. If you mirror logical drives in the same array and a physical drive fails, both logical drives in the mirrored pair will also fail. You will not be able to retrieve your data.

Because software-based drive mirroring is a function of the operating system, refer to the documentation included with your operating system for implementation.

Compaq recommends using hardware-based fault tolerance instead of software- based fault tolerance. Hardware-based fault tolerance provides a much more robust and controlled environment for fault-tolerance protection.

If you choose software-based drive mirroring, create at least two arrays with RAID 0 to achieve maximum storage capacity. Then, when you configure the drive mirroring through the operating system, mirror the logical drives residing in different arrays. In addition, the following fault-tolerant features will not be available: online spare, auto-reliability monitoring, interim data recovery, and automatic data recovery. See Chapter 5 for information on your drive array(s) and fault tolerance.