Redundant Copy; Figure 14 Redundant Copy Function - Fujitsu ETERNUS DX500 S4/DX600 S4 Design Manual

2. Basic Functions
Data Protection

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 decides that preventative maintenance is required for a drive, the data of the
maintenance target drive is re-created by the remaining drives and written to the hot spare. The Redundant
Copy function enables data to be restored while maintaining data redundancy.

Figure 14 Redundant Copy Function

RAID5 (Redundant)
RAID5 (Redundant)
Disconnected
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 assign-
ing an alternate track.
Redundant Copy speed
•
Giving priority to Redundant Copy over host access can be specified. By setting a higher Rebuild priority, the
performance of Redundant Copy operations may improve.
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.
FUJITSU Storage ETERNUS DX500 S4/DX600 S4, ETERNUS DX500 S3/DX600 S3 Hybrid Storage Systems Design Guide (Basic)
Sign of
Hot spare
failure
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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.
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