Abstract: A framework for converting between copy-on-write (COW) and redo-based technologies is disclosed. To take a virtual disk snapshot, disk descriptor files, which include metadata information about data stored in virtual volumes (vvols), are “swizzled” such that the descriptor file for a latest redo log, to which IOs are currently performed, points to the base vvol of a COW-based vvol hierarchy. A disk descriptor file previously associated with the base vvol may also be updated to point to the vvol newly created by the snapshot operation. To revert to an earlier disk state, a snapshot may be taken before copying contents of a snapshot vvol of the COW-based vvol hierarchy to a base vvol of the hierarchy, thereby ensuring that the reversion can be rolled back if it is unsuccessful. Reference counting is performed to ensure that vvols in the vvol hierarchy are not orphaned in delete and revert use cases.

Abstract: The storage system exports logical storage volumes that are provisioned as storage objects. These storage objects are accessed on demand by connected computer systems using standard protocols, such as SCSI and NFS, through logical endpoints for the protocol traffic that are configured in the storage system. Prior to issuing input-output commands to a logical storage volume, the computer system sends a request to bind the logical storage volume to a protocol endpoint. In response a first identifier for the protocol endpoint and a second identifier for the logical storage volume is returned. Different second identifiers may be generated for different logical storage volumes even though the same protocol endpoint is being used. Therefore, a single protocol endpoint may serve as a gateway for multiple logical storage volumes.