Hitachi 8450H/R - Manual (Page 54)

Ch 3: Installing Optional Devices
50 Hitachi PC VisionBase 8450H/R Server
Mirroring and Duplexing
You can save data in two hard disks to prepare for a possible hard disk failure. This dualized data structure is useful
in preventing data loss, because even if one hard disk fails, the other hard disk is still usable. There are two types of
dualizing data, mirroring and duplexing.
Mirroring
The same data is stored in two hard disks connected to the same SCSI board. Storing data requires more time than
non-dualized structure, because data is written successively onto the two hard disks.
Duplexing
Each of the two SCSI boards is connected to its hard disk into which the same data is written and stored at the same
time, resulting in a smaller reduction in processing speed.
NOTE: Hitachi PC VisionBase 8450H/R Server does not allow duplexing.