Qsan XS5224D User Manual page 174

Figure 8-43
Fast RAID Rebuild Notices
Here are some notices about Fast RAID Rebuild.
 Only a thick provisioning pool supports enabling/disabling this feature, a thin
provisioning pool has included this feature and set as enabled by default.
 When a rebuild occurs in a fast rebuild volume, clean partitions are not rebuilt since
there are no data saved there. Though clean partitions are never rebuilt, their health
status is good.
 If all partitions of the fast rebuild volume are clean, then no rebuild would happen and no
event would be sent.
The RAID stacks could not use optimize algorithm to compute parities of a partition

which is not rebuilt. Thus, the performance of random write in a clean partition would be
worse.
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Enable Fast RAID Rebuild When Creating a Volume
CAUTION:
Disabling Fast RAID Rebuild function is recommended when the access
pattern to the volume is random write.