Mapping Address Extent Sharing Management
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Solution Overview
Problem
Existing methods for managing extent sharing in software defined data centers, such as reference counting and shared bit methods, suffer from high IO overhead and performance issues when deleting snapshots or overwriting extents, as they require extensive metadata scans and operations.
Innovation Solution
The proposed solution involves using a monotonically increasing mapping address (MBA) for each extent and a snapshot mapping address (SSMBA) to simplify extent sharing management, eliminating the need for reference counts and shared bits, thereby reducing IO overhead and improving performance during snapshot deletion and extent overwrite operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference counting or shared bit methods are used to manage extent sharing, then extent ownership can be tracked, but IO overhead increases and performance deteriorates during snapshot deletion and extent overwrite operations
Solution Approach 1:
The patent extracts and eliminates the reference counting mechanism and shared bit fields from the extent metadata structure. By removing these unnecessary tracking components, the system achieves extent ownership determination through a simpler mapping address comparison approach, thereby reducing metadata operations and IO overhead during snapshot deletion and extent overwrite operations.
Solution Approach 2:
Instead of actively tracking extent sharing status through reference counts and shared bits, the patent inverts the approach by using mapping addresses to passively determine ownership. Extent ownership is inferred by comparing mapping addresses rather than actively managing sharing state, which reverses the traditional tracking paradigm and reduces operational complexity.
2Reliability
If reference counting and shared bit methods are used, then extent sharing can be managed, but metadata scans and operations become extensive, increasing IO overhead
Solution Approach 1:
The patent removes the reference counting fields and shared bit metadata from the extent structure, eliminating the need for extensive metadata scans. Ownership determination is achieved through direct mapping address comparison, significantly reducing the amount of metadata processing and associated IO operations required during snapshot deletion and extent overwrite.
Solution Approach 2:
The patent uses mapping address copies and comparisons instead of active metadata tracking. By maintaining mapping addresses that encode ownership information and comparing these addresses during operations, the system avoids the need for extensive metadata scanning while achieving the same ownership determination reliability.
Data Source
AI summary
The present disclosure is related to methods, systems, and machine-readable media for managing extent sharing between snapshots using mapping addresses. A first mapping address can be assigned to a first extent responsive to a request to write the first extent. A second mapping address can be assigned to a second extent responsive to a request to write the second extent. A snapshot can be created. A snapshot mapping address, that is monotonically increased from the second mapping address, can be assigned to the snapshot. A third mapping address, that is monotonically increased from the second mapping address, can be assigned to a third extent of the snapshot responsive to a request to write the third extent. An ownership status of each of the first extent, the second extent, and the third extent can be determined based respectively on: a comparison between the first mapping address and the snapshot mapping address, a comparison between the second mapping address and the snapshot mapping address, and a comparison between the third mapping address and the snapshot mapping address.