Copyback/Copybackless; Figure 14 Copyback - Fujitsu ETERNUS DX S5 Series Design Manual

2. Basic Functions
Data Protection

Copyback/Copybackless

A Copyback process copies data in a hot spare to the new drive that is used to replace the failed drive.
Figure 14 Copyback
Failed drive
Copyback
IMPORTANT
• Copyback speed
Giving priority to Copyback over host access can be specified. By setting "Rebuild Priority" to "High",
Copyback operations are given priority over host access and the performance of the Copyback operations
may improve.
However, it should be noted that when the priority is high and a Copyback 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.
If copybackless is enabled, the drives that are registered in the hot spare become part of the RAID group
configuration drives after a rebuild or a redundant copy is completed for the hot spare.
The failed drive is disconnected from the RAID group configuration drives and then registered as a hot spare.
Copyback is not performed for the data even if the failed drive is replaced by a new drive because the failed drive
is used as a hot spare.
A copyback operation is performed when the following conditions for the copybackless target drive (or hot
spare) and the failed drive are the same.
Drive type (SAS disks, Nearline SAS disks, SSDs, and Self Encrypting Drives [SEDs])
•
RAID5 (Redundant)
RAID5 (Redundant)
RAID5 (Redundant)
After rebuilding has been completed,
replaces the failed drive with the new drive.
After replacing has been completed,
copies the data from the hot spare
to the new drive.
Hot spare
53 Design Guide