Managing a deletion of a volume referenced by a snapshot of a consistency group
First Claim
1. A method of managing a deletion of volume referenced by a snapshot of a consistency group, the method comprising:
- designating a to-be deleted original volume as a ghost volume within a consistency group stored within a storage system, the consistency group, subsequent to the designation of the ghost volume, comprising the ghost volume and a plurality of original volumes;
identifying a preexisting point-in-time snapshot of the consistency group that existed prior to the designation of the ghost volume, the preexisting point-in-time snapshot, subsequent to the designation of the ghost volume, comprising a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group and an orphaned pointer that points to the ghost volume;
subsequent to the designation of the ghost volume, taking a present point-in-time snapshot of the consistency group, the present point-in-time snapshot consisting of a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group; and
preventing deletion of the ghost volume from the storage system until there are no point-in-time snapshots of the consistency group that comprise a orphaned pointer that points to the ghost volume.
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Abstract
When a volume that was once associated with a consistency group and is to be deleted from the storage system, the to be deleted volume is designated as a ghost volume within the storage system, and the deletion of the ghost volume from the storage system is delayed until there are no snapshots that include a pointer to the ghost volume. The storage system may include a counter that counts the number of instances all volumes within a consistency group are pointed to or that counts the number of instances that only ghost volumes are pointed to. The storage system may reference this count to determine whether to immediately delete or delay the deletion of the volume from the storage system.
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Citations
20 Claims
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1. A method of managing a deletion of volume referenced by a snapshot of a consistency group, the method comprising:
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designating a to-be deleted original volume as a ghost volume within a consistency group stored within a storage system, the consistency group, subsequent to the designation of the ghost volume, comprising the ghost volume and a plurality of original volumes; identifying a preexisting point-in-time snapshot of the consistency group that existed prior to the designation of the ghost volume, the preexisting point-in-time snapshot, subsequent to the designation of the ghost volume, comprising a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group and an orphaned pointer that points to the ghost volume; subsequent to the designation of the ghost volume, taking a present point-in-time snapshot of the consistency group, the present point-in-time snapshot consisting of a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group; and preventing deletion of the ghost volume from the storage system until there are no point-in-time snapshots of the consistency group that comprise a orphaned pointer that points to the ghost volume. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A computer program product for managing a deletion of a volume referenced by a snapshot of a consistency group, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions readable by a storage system to cause the storage system to:
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designate a to-be deleted original volume as a ghost volume within a consistency group stored within the storage system, the consistency group, subsequent to the designation of the ghost volume, comprising the ghost volume and a plurality of original volumes; identify a preexisting point-in-time snapshot of the consistency group that existed prior to the designation of the ghost volume, the preexisting point-in-time snapshot, subsequent to the designation of the ghost volume, comprising a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group and an orphaned pointer that points to the ghost volume; subsequent to the designation of the ghost volume, take a present point-in-time snapshot of the consistency group, the present point-in-time snapshot consisting of a plurality of pointers that each point to a different one of the plurality of original volumes of the consistency group; and prevent deletion of the ghost volume from the storage system until there are no point-in-time snapshots of the consistency group that comprise a orphaned pointer that points to the ghost volume. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A storage system comprising:
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a consistency group repository comprising a consistency group that comprises a plurality of original volumes and a designated ghost volume; a snapshot repository comprising; a first point-in-time snapshot of the consistency group taken prior to the designation of the ghost volume, the first point-in-time snapshot comprising a first plurality of pointers that each point to a different one of the plurality of original volumes and an orphaned pointer that points to the ghost volume; a second point-in-time snapshot of the consistency group taken subsequent to the designation of the ghost volume, the second point-in-time snapshot consisting of a second plurality of pointers that each point to a different one of the plurality of original volumes; and a snapshot manager stored upon a computer readable storage medium within the storage system that when called by the storage system, causes the storage system to prevent deletion of the ghost volume from the storage system until there are no point-in-time snapshots of the consistency group that comprise a orphaned pointer that points to the ghost volume. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification