Compaq 386 manual Mass Storage Configuration, Theory of Operation

Chapter 9

MASS STORAGE CONFIGURATION

Maintenance and Service Guide 9-1

9.1 THEORY OF OPERATION

The 300-/600-Megabyte Fixed Disk Drive Expansion Unit can be used with a COMPAQ DESKPRO 386-based Personal Computer with system ROM revision G or later. The expansion unit can be used as a normal external fixed disk drive for maximum storage or in a mirroring or duplexing mode. The three options are described below:

□Maximum storage. This gives you the maxi- mum storage space available in the drives.

Example: With dual 300-Megabyte fixed disk drives installed in the expansion unit, you would have a total storage capability of 600 megabytes of information. Two expansion units configured this way would give you a maximum of 1.2 gigabytes of storage.

□Mirroring. In mirroring, two identical fixed disk drives are connected to a single con- troller. Special software causes both drives to read and write the same information.

Example: In this case, the same two 300 megabyte drives would only have a total storage capability of 300 megabytes, since the two drives would contain exactly the same information. However, this in turn would keep the system operational and the stored data intact if the hardware for one fixed disk drive failed.

Addendum 108431-001 (11-88) to Manual No. 108033-003