Delta Storage Structure for Stun-Free Virtual Volume Snapshots
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Solution Overview
Problem
Conventional storage arrays struggle to apply storage policies and management operations on a per-VM basis in virtualized deployments due to the inability to distinguish between virtual machines, leading to long stun times during snapshot creation, which negatively impact system performance.
Innovation Solution
Implementing delta storage structures for each virtual volume to be snapshotted, allowing write I/Os to be directed and stored during snapshot generation without pausing VM execution, and subsequently merging these changes back into the original volumes, enabling continuous I/O operations and improved system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional storage arrays use per-LUN/file system volume storage management, then storage policies can be applied at the LUN level, but the system cannot distinguish between multiple VMs sharing the same LUN and thus cannot apply per-VM storage policies
Solution Approach 1:
The patent segments the storage management unit from the traditional LUN level down to the virtual volume level. Each virtual volume is assigned a unique identifier and can be independently managed, allowing per-VM storage policies to be applied. This segmentation enables the storage array to distinguish between multiple VMs sharing the same LUN and apply differentiated storage policies to each VM's data.
2Manufacturing precision
If VMs are stunned to capture their state for snapshots, then consistent snapshots can be taken, but VM execution is paused and I/O operations are frozen during snapshot creation
Solution Approach 1:
The patent performs preliminary actions by creating a delta storage structure before the actual snapshot is taken. This delta structure is prepared in advance to receive and store I/O operations that occur during the snapshot process. By having this structure ready beforehand, the system can capture consistent state information without needing to pause VM execution, as the delta structure will accommodate any I/O operations that occur during snapshot creation.
Solution Approach 2:
The delta storage structure acts as an intermediary between the VM's I/O operations and the snapshot process. Instead of directly freezing I/O operations to achieve consistency, the delta structure mediates by capturing I/O operations in a separate structure during snapshot creation. This allows the snapshot to capture a consistent point-in-time state while I/O operations continue to be processed and stored in the delta structure, eliminating the need to pause VM execution.
3Measurement precision
If I/O operations are frozen during snapshot creation to ensure consistency, then accurate snapshots can be taken, but write I/Os cannot be committed during the snapshot process
Solution Approach 1:
The patent enables the continuity of useful action by allowing I/O operations to continue being processed and committed during snapshot creation. The delta storage structure is designed to receive and commit write I/Os in real-time during the snapshot process, eliminating the need to freeze I/O operations. This continuous operation ensures that the snapshot captures an accurate point-in-time state while maintaining full I/O operational continuity, as all writes are committed to the delta structure without interruption.
4Reliability
If long stun times are used during snapshot creation to ensure data consistency, then complete snapshots can be taken, but system performance is negatively impacted
Solution Approach 1:
The patent uses copying by creating a delta storage structure that is a copy of the virtual volume's storage structure. This delta copy is created in advance and is used to store I/O operations during snapshot creation. By working with this copy rather than the original volume, the system can capture consistent state information without needing to pause VM execution or use long stun times. The delta structure serves as a temporary copy that accommodates all I/O operations during the snapshot process, enabling fast snapshot creation with maintained data consistency.
Data Source
AI summary
The disclosure provides a method for virtual volume snapshot creation by a storage array. The method generally includes receiving a request to generate a snapshot of a virtual volume associated with a virtual machine, in response to receiving the request, preparing a file system of the storage array to generate the snapshot, wherein preparing the file system comprises creating a delta storage structure to receive write input/output (I/O) requests directed for the virtual volume when generating the snapshot of the virtual volume, deactivating the virtual volume, activating the delta storage structure, generating the snapshot of the virtual volume, and during the generation of the snapshot of the virtual volume: receiving a write I/O directed for the virtual volume and committing the write I/O in the delta storage structure.