Rebuild
Rebuild processes recover data in failed drives by using other drives. If a free hot spare is available when one of the RAID group drives has a problem, data of this drive is automatically replicated in the hot spare. This ensures data redundancy.
![](../../image/sekkei/rebuild.png)
When no hot spares are registered, rebuilding processes are only performed when a failed drive is replaced or when a hot spare is registered.
Rebuild Speed
The priority of the rebuild operations with respect to host access can be specified. By setting "Rebuild Priority" to "High", rebuild operations are given priority over host access and the performance of the rebuild operations may improve.
However, it should be noted that when the priority is high and a rebuild operation is performed for a RAID group, the performance (throughput) of this RAID group may be reduced.
Refer to "Modify RAID Group Parameters" in "Web GUI User's Guide" for details.