Copyback/Copybackless; Figure 16 Copyback - Fujitsu ETERNUS DX100 S4 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 16 Copyback

Failed drive
Copyback
Copyback speed
•
Giving priority to Copyback over host access can be specified. By setting a higher Rebuild pri-
ority, the performance of Copyback operations may improve.
However, it should be noted that when the priority is high and a Copyback operation is per-
formed for a RAID group, the performance (throughput) of this RAID group may be reduced.
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])
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Fujitsu Storage ETERNUS DX100 S4/DX200 S4, ETERNUS DX100 S3/DX200 S3 Hybrid Storage Systems Design Guide (Basic)
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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
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