Multi-Tier Virtual Disk Snapshot Quiesce Mechanism
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Solution Overview
Problem
Current methods for saving data in a multi-tiered virtual storage space while active are inadequate, as there is no defined process to prepare the hosted operating system for backup, leading to inconsistent data and the need for system shutdowns to ensure data integrity, especially when hosting multiple operating systems like Microsoft virtual servers or VMWare.
Innovation Solution
A method involving a two-phase process, 'Freeze' and 'Thaw', where servers in lower tiers are instructed to quiesce applications, obtain and store data in temporary storage, and then resume operations, allowing for a snapshot of the object using a copy-on-write approach, ensuring data consistency and enabling active storage space saving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hosted operating system is shut down to save storage space, then data consistency is ensured, but system availability is reduced
Solution Approach 1:
The patent applies preliminary action by initiating a quiesce phase before the actual snapshot operation. During this phase, lower-tier operating systems are notified to flush their caches and prepare for the snapshot, ensuring data consistency is established beforehand. This allows the upper-tier OS to be saved without requiring a complete shutdown, thus maintaining system availability while ensuring data integrity through pre-prepared consistent state.
2Reliability
If a snapshot is taken of the storage space, then data at the snapshot point is preserved, but data consistency may be compromised due to ongoing writes
Solution Approach 1:
The patent segments the storage system into multiple tiers with distinct operating systems at different levels. Each tier can be independently managed and quiesced. When a snapshot is needed at an upper tier, only that specific tier and its dependent lower tiers are quiesced, while other unrelated tiers continue operating. This segmentation allows partial snapshots without requiring complete system shutdown, preserving snapshot accuracy while minimizing data inconsistency risks.
Solution Approach 2:
The patent implements preliminary action through a quiesce phase that is initiated before the actual snapshot operation. During this phase, lower-tier operating systems are notified to flush their caches and prepare for the snapshot, ensuring data consistency is established beforehand. This allows the upper-tier OS to be saved without requiring a complete shutdown, thus maintaining system availability while ensuring data integrity through pre-prepared consistent state.
3Reliability
If cache data is written to disk before saving, then data consistency is improved, but save time is increased
Solution Approach 1:
The patent applies preliminary action by initiating a quiesce phase before the actual snapshot operation. During this phase, lower-tier operating systems are notified to flush their caches and prepare for the snapshot, ensuring data consistency is established beforehand. This allows the upper-tier OS to be saved without requiring a complete shutdown, thus maintaining system availability while ensuring data integrity through pre-prepared consistent state.
Solution Approach 2:
The patent implements a dynamic multi-phase save process that adapts to the system state. The quiesce phase is dynamic in that it only affects the necessary lower tiers required for the specific snapshot operation, rather than forcing a complete system-wide cache flush. This dynamic approach minimizes the time impact while still ensuring the necessary data consistency for the targeted storage space save.
Data Source
AI summary
An object in a tier of a multi-tier virtual storage system is saved while the storage system is active. The object to be saved in an upper-level tier in the multi-tier storage system is identified. Servers associated with lower-level tiers below the tier containing the object to be saved to obtain the latest data stored in the respective associated tiers, use temporary storage to store the obtained data and handle any modifications to the obtained data, and cause applications running in the respective tiers to quiesce. Once a copy of the identified object is made, the servers associated with the lower-level tiers are instructed to obtain the data from the temporary storage and resume quiesced applications running in the respective tiers.