Snapshot Consolidation via I/O Mirroring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The performance of read I/O operations in virtual machines is negatively impacted by the increased number of delta disks resulting from multiple snapshots, leading to degraded I/O performance and potential consolidation failures due to high I/O and CPU resource costs during consolidation processes.
Innovation Solution
A mirror driver is interposed between the current running disk and the target disk during consolidation, allowing for synchronous mirroring of writes and copying of disk sectors in a single pass without requiring helper disks, thereby ensuring convergence and minimizing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple snapshots are created to preserve virtual disk states, then data preservation capability is improved, but read I/O performance deteriorates due to increased number of delta disks to traverse
Solution Approach 1:
The patent extracts the harmful element (redundant delta disks) from the system by identifying and consolidating delta disks that correspond to snapshots no longer needed for data preservation, thereby removing the performance bottleneck while maintaining necessary data protection capabilities
Solution Approach 2:
The patent merges multiple delta disks into a single consolidated delta disk by copying data from multiple source delta disks to a destination delta disk, reducing the number of layers in the delta disk chain and improving read I/O performance while preserving data from all necessary snapshots
2Device complexity
If delta disks are consolidated by copying data from source to destination, then redundant delta disks are reduced, but I/O and CPU resource consumption increases significantly
Solution Approach 1:
The patent performs preliminary identification of redundant delta disks using heuristics (such as checking if source delta disks are not the latest and have no dependent snapshots) before consolidation, allowing the system to avoid consolidating non-redundant disks and thus reduce unnecessary I/O and CPU resource consumption
Solution Approach 2:
The patent changes the consolidation approach by implementing incremental consolidation that processes only identified redundant delta disks with smaller data sets, rather than consolidating all delta disks, thereby reducing the overall I/O and CPU resource requirements while still achieving the goal of reducing delta disk count
3Reliability
If large data sets are copied during consolidation, then complete data migration is achieved, but I/O performance degradation becomes severe and consolidation may fail
Solution Approach 1:
The patent applies partial action by consolidating only the specific redundant delta disks identified through heuristics, rather than consolidating all delta disks or all data, thereby reducing the scope of data copying and minimizing I/O performance degradation while still achieving successful consolidation of necessary redundant data
Data Source
AI summary
To create a backup of a live (running) virtual machine, a backup agent may take a snapshot of the virtual machine, backup the virtual machine from the snapshot disk, and delete the snapshot. Deleting the snapshot initiates a snapshot consolidation process where delta disks of the virtual machine are collapsed. A virtual disk layer sets up a mirror driver between a current virtual disk and a target virtual disk. Data sectors of the delta disk are copied over to the target virtual disk in a single pass, while the mirror driver mirrors write request for the current virtual disk to the target virtual disk.