3Com SuperStack 3 NBX Administrator's Manual page 342

342 C 5: S C
HAPTER YSTEM ONFIGURATION
When the mirror disk is fully partnered with the master system disk, all
data that is written to the master disk is also written to the mirror disk. If
data is read from disk, the software has the option of reading from either
disk, which can improve data access times.
If either disk fails in a fully mirrored system, the system software switches
to use only the remaining good disk, and system operation continues.
Status information is available on the Call Processor front panel LEDs to
indicate when a disk has failed and which disk to replace. After you
replace a failed disk and restart the system, the software starts bringing
the new disk up to a fully mirrored state. The system typically takes from
30 to 90 minutes to complete the mirroring process, depending on the
amount of data on the master disk.