Zero data page reclaim is the action of reclaiming volume pages whose data is only zeros. This can reduce volume and storage pool usage.
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Zero data page reclaim is performed in units of pages (42 [MiB]).
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Zero data page reclaim takes approximately one minute per 4 [GiB]. Depending on the storage cluster configuration and whether zero data pages are present, this process may complete faster.
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The following pages are not reclaimed.
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Pages containing control information
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Pages containing data (pages except for zero data pages)
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You can perform zero data page reclaim for P/S-VOLs and S-VOLs of snapshots. However, this does not reduce P/S-VOL and S-VOL usage.
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When zero data page reclaim is performed on a volume with data reduction enabled, fixed pattern exclusion (by the data reduction function) is applied to the relevant area, and zero data page reclaim is not performed. As a result, usage of the storage pool containing the volume is reduced, but usage of the volume itself is not reduced.
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Zero data page reclaim performed as a countermeasure for capacity depletion has the following characteristics:
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System configuration does not change because the volume remains.
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The process takes longer than volume deletion.
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Data reduction is not performed if no zero-data pages exist.
If you want to resolve capacity depletion securely as soon as possible, consider deleting unnecessary volumes.
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If you performed zero data page reclaim with a wrong volume specified or you want to prioritize other operations, you can stop zero data page reclaim. For details about how to stop zero data page reclaim, see Stopping zero data page reclaim of volumes.