Redundant Copy; Figure 11 Redundant Copy Function - Fujitsu ETERNUS DX S5 Series Design Manual

2. Basic Functions
Data Protection
Caution
The Maintenance Operation privilege is required to set detailed parameters.

Redundant Copy

Redundant Copy is a function that copies the data of a drive that shows a possible sign of failure to a hot spare.
When the Disk Patrol function determines that a drive requires preventative maintenance, the data of the
maintenance target drive is recreated by the remaining drives and written to the hot spare. The Redundant Copy
function enables data to be restored while maintaining data redundancy.
Figure 11 Redundant Copy Function
RAID5 (Redundant)
RAID5 (Redundant)
Disconnected
Note
If a bad sector is detected when a drive is checked, an alternate track is automatically assigned. This drive
is not recognized as having a sign of drive failure during this process. However, the drive will be
disconnected by the Redundant Copy function if the spare sector is insufficient and the problem cannot be
solved by assigning an alternate track.
IMPORTANT
• Redundant Copy speed
The priority of the Redundant Copy with respect to host access can be specified. By increasing the
Rebuild priority, the Redundant Copy operation is given a higher priority than the host access and the
performance of the Redundant Copy operation is improved.
However, it should be noted that when the priority is high and a Redundant Copy operation is
performed for a RAID group, the performance (throughput) of this RAID group may be reduced.
Refer to "Modify RAID Group Parameters" in "ETERNUS Web GUI User's Guide" for details.
Sign of
Hot spare
failure
50
Creates data from the drives other than
the maintenance target drive, and
writes data into the hot spare.
Disconnects the maintenance target drive
and switches it to the hot spare.
Design Guide