Emc IP Holding Company LLC

Shruti Gupta

Michael Ferrari

George F Lettery

Jeffrey Wilson

Sandeep Chandrashekhara

Nicholas W Von Hein

Snapshot metadata may include a plurality of pages of nodes, including active nodes and free nodes. It may be determined whether a snapshot metadata object is eligible for de-allocation, for example, of one or more of the pages of its snapshot metadata nodes. This determination may be based on a number of free nodes in the snapshot metadata object, for example, in relation to the quantity of nodes that are included in a snapshot metadata page. This determination may be made based on previous usage of the nodes allocated to the snapshot metadata object, for example, the number of active nodes relative to a total size of the snapshot metadata object. For example, a maximum extent of active nodes during one or more periods may be compared to a current extent of active nodes to determine whether the snapshot metadata object is eligible.

Efficient memory usage for snapshots based on past memory usage

Memory may be used more efficiently for snapshot metadata by reducing a size of a snapshot metadata object, for example, by removing free nodes from the snapshot metadata object. Removing free nodes may include consolidating free nodes into a single page of a snapshot metadata object and de-allocating the page from the memory allocated for the data structure. Consolidation of free nodes may be achieved by identifying active nodes in the single page, and swapping these active nodes with free nodes from other pages until the single page includes only free nodes. The nodes of the single page that were already free and the active nodes that were swapped with free nodes from another page may be designated for de-allocation. This designating may result in all nodes of the single page being designated for de-allocation, after which the single page of nodes may be de-allocated.

Efficient memory usage for snapshots

Techniques for providing snapshots of logical devices may include: receiving a first request to create a first snapshot of a logical device; responsive to the first request, performing first processing including storing first information in a cache slot, the first information identifying the first snapshot and the logical device used as a source of the first snapshot; receiving a second request to activate one or more snapshots, including the first snapshot, identified by information stored in the cache slot; and responsive to receiving the second request, performing second processing including initiating execution of an asynchronous process that performs snapshot activation processing for the one or more snapshots identified by the cache slot.

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Hopkinton, MA, United States of America

Shruti Gupta