Virtual disk snapshot consolidation using block merge

摘要

A virtualized computer system employs a virtual disk. Multiple snapshots of the virtual disk can be created. After a snapshot is created, writes to the virtual disk are captured in delta disks. Two snapshots are consolidated by updating block references in snapshot meta data. Block reference update takes advantage of the fact that blocks for the two snapshot are managed within the same storage container and, therefore, can be moved in the snapshot logical space without incurring data copy operations. Consolidation of delta disks also gracefully handles failures during the consolidation operation and can be restarted anew after the system has recovered from failure.

主权项

1. A method for consolidating a plurality of delta disks included in a delta disk chain associated with a virtual disk, the method comprising:
determining that a first delta disk included in the delta disk chain is to be consolidated with a second delta disk included in the delta disk chain, wherein, once consolidated, the second delta disk is to be removed from the delta disk chain; determining that a first data block in the first delta disk corresponds to a second data block in the second delta disk, wherein the second data block stores data reflecting an update to data stored in the first data block; and modifying a reference included in metadata for the first delta disk that points to the first data block to point to a second data block included in the second delta disk, while maintaining a reference included in metadata for the second delta disk that points to the second data block.