Software-Based Drive Mirroring - Compaq Smart Array 221 User Manual

C-22 Understanding Drive Arrays

Software-Based Drive Mirroring

IMPORTANT: Compaq strongly 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.
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 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.
For more information on hardware versus software fault tolerance, see the
White Paper section of the Compaq Storage website.
Writer: Karen Hale Project: Compaq Smart Array 221 Controller User Guide Comments: 388541-001
File Name: K-APPC.DOC Last Saved On: 11/5/98 1:40 PM
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