VSS Provider Snapshotting Virtual Volumes via Identifier Mapping
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Solution Overview
Problem
The existing methods for snapshotting virtual machines using Volume Shadow Copy Service (VSS) face challenges in operating with virtual volumes (VVOLs, as they require mapping between different identifiers and ensuring application consistency, leading to difficulties in capturing the state of virtual machines effectively.
Innovation Solution
Configuring VSS components to operate with VVOLs by mapping VVOL identifiers to logical unit identifiers and vice versa, and using VSS requester and provider to quiesce applications and flush buffer caches, ensuring application consistency during snapshot operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VSS components are configured to operate with VVOLs using identifier mapping, then snapshot capability for virtual machines is enabled, but system complexity increases due to mapping requirements
Solution Approach 1:
The patent introduces a mapping system that acts as an intermediary between VVOL identifiers and logical unit identifiers. This mapping mechanism enables the VSS components to operate with VVOLs without directly managing the complexity of identifier translation, as the mapping system handles the conversion automatically.
Solution Approach 2:
The VSS requester and provider are configured to handle multiple identifier types (VVOL identifiers and logical unit identifiers) through a universal mapping interface. This multi-functionality allows the same VSS components to work with different storage identifier schemes without requiring separate implementation paths.
2Reliability
If applications are quiesced and buffer caches are flushed to ensure application consistency, then data consistency during snapshot is improved, but operation time increases
Solution Approach 1:
The VSS writer component performs preliminary actions by quiescing applications and flushing buffer caches before the actual snapshot operation. This preliminary preparation ensures that when the snapshot is taken, all data is in a consistent state, preventing the need for corrective actions after the snapshot.
Solution Approach 2:
The system implements feedback mechanisms where the VSS writer monitors application state and buffer cache status, coordinating with the VSS requester to determine when the system is ready for snapshot. This feedback loop ensures data consistency while allowing the process to proceed as quickly as possible once consistency is achieved.
Data Source
AI summary
Described herein are techniques for configuring a volume shadow copy service (VSS) requester and/or VSS provider so that a snapshot may be taken of application data stored on a virtual volume (VVOL). The VSS requester may receive a request to take a snapshot of a VVOL, the VVOL identified by a VVOL identifier. The VSS provider associated with a storage array may determine whether the storage array supports taking the snapshot of the VVOL. The determination may be based on information derived from a mapping which maps respective VVOL identifiers to respective logical unit identifiers. If the VSS provider supports taking the snapshot of the VVOL, the VSS provider may take the snapshot of the VVOL.