Host-Level VSS Writer for Application-Consistent VM Backups
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Solution Overview
Problem
Existing systems face challenges in creating application-consistent backups of virtual machines without interrupting their operation, especially in virtualized server environments, where pausing or turning off virtual machines is undesirable and installing backup agents for each virtual machine is costly and resource-intensive.
Innovation Solution
A host server writer instructs virtual machines to create application-consistent snapshots, and the backup application on the host server creates snapshots of host-level volumes, allowing for consistent backups without significant interruptions or the need for additional backup agents, by utilizing existing backup requestors and writers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a host creates a snapshot or backup copy of virtual machine volumes, then backup data can be obtained, but the data may not be application-consistent because processes inside the virtual machine continue to run
Solution Approach 1:
The patent introduces a host-level VSS writer as an intermediary component that mediates between the backup application and the virtual machine processes. This writer intercepts and coordinates snapshot operations, ensuring that application-consistent backups are achieved without requiring direct intervention from virtual machine applications. The intermediary handles the complexity of coordinating multiple processes while maintaining operational simplicity for the end user.
Solution Approach 2:
The patent segments the backup system into distinct functional components: the backup application, the host-level VSS writer, and the virtual machine processes. By dividing the system into these segments with clearly defined interfaces, the patent enables application-consistent backups through coordinated operation of independent components, resolving the contradiction between reliability and ease of operation.
2Reliability
If backup agents are installed in each virtual machine to create application-consistent snapshots, then application-consistent backups can be achieved, but the cost and resource expenditure increase significantly
Solution Approach 1:
The patent implements a universal host-level VSS writer that serves all virtual machines on the host system. This single multi-functional component replaces the need for multiple individual backup agents, achieving application-consistent backups across all virtual machines while significantly reducing the quantity of software required. The universal writer coordinates snapshots for multiple virtual machines through a standardized interface.
Solution Approach 2:
The patent merges the backup functionality into the host system level, combining what would otherwise require separate backup agents in each virtual machine into a single centralized solution. By merging these functions at the host level, the patent reduces resource expenditure while maintaining application-consistency through coordinated control of all virtual machine snapshots.
3Reliability
If virtual machines are paused or turned off to create consistent backups, then application-consistency is achieved, but virtual machine availability and productivity decrease
Solution Approach 1:
The patent employs preliminary action by having the host-level VSS writer prepare and coordinate snapshot operations before the actual backup process begins. The writer pre-establishes the necessary conditions for application-consistent snapshots and manages the timing of snapshot creation, allowing backups to proceed without interrupting virtual machine operation. This preliminary coordination ensures consistency while maintaining availability.
Solution Approach 2:
The patent enables continuous operation of virtual machines during the backup process by maintaining the useful action of process execution throughout the snapshot operation. The host-level VSS writer manages the snapshot creation in a way that does not interrupt or pause virtual machine processes, ensuring both application-consistency and continuous productivity without downtime.
Data Source
AI summary
A host server hosting one or more virtual machines can back up host volumes and the one or more virtual machines installed thereon in an application-consistent manner. In one implementation, a host-level requestor instructs a host-level writer to identify which virtual machines qualify for application-consistent backups. The host-level requestor then instructs the host-level writer to initiate virtual machine backups through guest-level requesters in each appropriately-configured virtual machine, wherein the virtual machines create application-consistent backups within the virtual machine volumes. The host-level requester then initiates snapshots of the server volumes on the host-level. The virtual machine-level snapshots can thus be retrieved from within the host-level snapshots of the server volumes.