Theory of Operation
The Tape RAID Level-1
operation is referred to as "Tape Mirroring" (or data duplication). Each
block of the users data is written to a specific set of array channels (referred to as a
"Mirrored set") at the same time. The controller maintains the tape
positions for all drives within a mirrored set (up to 5 drives).User data is read from the lowest channel number within the mirrored
set. The array controller handles read/write errors differently depending on the
settings of the disaster recovery options.
If a write error is encountered with any one of the drives
within a mirrored set and the fault tolerant write option is enabled, the failing drive is
disabled on the fly without interrupting the backup process. The controller reports
a write error only upon detecting a write error from "all of the drives" within
a mirrored set.
If a write error is encountered with any one of the drives
within a mirrored set and the fault tolerant write option is disabled, the write error is
reported to the host.
If a read error is encountered with any one of the drives
within a mirrored set and the fault tolerant read option is enabled, the failing drive is
disabled on the fly without interrupting the restore or verify process. The
controller reports a read error only upon detecting a read error from "all of the
drives" within a mirrored set.
If a read error is encountered with any one of the drives
within a mirrored set and the fault tolerant read option is disabled, the read error is
reported to the host. The array controller does not attempt to recover read errors
using other available drives within the mirrored set. |
