Conversion of virtual disk snapshots between redo and copy-on-write technologies
US9116737B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 2013 |
| Grant date | Aug 25, 2015 |
| Priority date | — |
| Expiry date | Oct 18, 2033 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2201/84
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
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. Differences between vvols in the COW-based vvol hierarchy are used to clone the hierarchy and to migrate the hierarchy to a redo-based disk hierarchy.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.