Hierarchical Storage Snapshot Management Without Tape Recall

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Solution Overview

Problem

Existing snapshot methods in storage systems are ineffective for creating and managing snapshots of hierarchically managed logical volumes when valid data is present on physical tape but not on disk, as they require immediate recall of data to disk, which is impractical due to limited disk cache capacity and time constraints.

Innovation Solution

A method that uses a management table to track the creation, migration, and storage status of logical volumes, allowing snapshots to be created and managed without immediate recall from second-level storage to first-level storage, by updating metadata to reflect migration and storage location, and only recalling data when access is requested.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional snapshot methods are used for hierarchically managed logical volumes, then snapshots can be created when data is present on disk, but snapshots cannot be created when data has migrated to physical tape

Engineering Contradiction:

Improvesnapshot creation capabilityVSAvoidsnapshot management reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the snapshot management process into distinct phases: snapshot registration phase (where metadata is created and stored in management tables) and snapshot realization phase (where actual snapshot data is retrieved). This allows the system to accept snapshot requests for migrated data without immediately recalling it from tape, separating the acceptance of the snapshot request from the actual data retrieval operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary actions by creating and storing snapshot metadata in management tables during the snapshot registration phase, before the actual snapshot data is recalled from tape. The management tables pre-record the logical volume information, snapshot time, and storage location, enabling the snapshot to be properly managed and tracked even before the physical data is available on disk.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If data is immediately recalled from physical tape to disk to create snapshots, then snapshots can be created for migrated data, but disk cache capacity is exceeded and system performance degrades

Engineering Contradiction:

Improvesnapshot creation reliabilityVSAvoiddisk cache capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies partial action by recalling only the specific logical volume data needed for the snapshot operation from physical tape, rather than recalling all migrated data. The system selectively retrieves only the portions of data required for the snapshot, leaving other migrated data on tape, thus avoiding excessive disk cache usage while still enabling snapshot creation.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If data is recalled from physical tape to disk for snapshot creation, then snapshots can be created for migrated data, but system response time increases due to tape recall operations

Engineering Contradiction:

Improvesnapshot creation reliabilityVSAvoidsnapshot creation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamic snapshot management where the system can handle snapshot requests for migrated data by updating management tables immediately, and the actual data retrieval is dynamically triggered only when the snapshot data is actually needed for access or restoration operations, rather than immediately recalling all data.

Inventive Principle:

Principle #15Dynamics

4Productivity

If simple pointer information is used for snapshot management, then disk-level snapshots can be created efficiently, but hierarchical snapshot management across disk and tape is not possible

Engineering Contradiction:

Improvesnapshot creation efficiencyVSAvoidhierarchical storage support

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal management table structure that can handle both disk-based and tape-based logical volumes through a unified interface. The management tables store metadata that is applicable regardless of whether the underlying data resides on disk or tape, enabling the same snapshot management mechanisms to work across hierarchical storage levels. The system universally manages snapshots by recording logical volume information and storage location in the management tables, making the snapshot functionality adaptable to different storage media.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9665436B2Creation and management of logical volume snapshots under hierarchical storage system

Publication Date: 2017.05.30 MEDIATEK INC

AI summary

The method of the present invention includes the steps of: receiving a command for creating a snapshot of the logical volume; preparing a management table for managing the snapshot; detecting the storage status of the logical volume; and updating the management table without recalling the logical volume from the second level storage to the first level storage when the logical volume has migrated from the first level storage to the second level storage. After the update, the storage table indicates whether creation of a snapshot is required, whether a logical volume has migrated, and whether the second level storage is the storage location of the logical volume.