Storage System Last Allocated Page Identification

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Solution Overview

Problem

In distributed storage systems, corrupted anchor pages can lead to inaccurate identification of the last allocated page for the map, resulting in overwriting valid data or orphaning storage space, especially during reinitialization and recovery processes, due to the inability to accurately determine the end of allocated storage.

Innovation Solution

The method involves storing a timestamp associated with the most recent reinitialization in superblocks and anchor pages, using this timestamp and a marker to identify the last allocated page, and ensuring accurate allocation by scanning for pages with the correct timestamp and marker, thereby preventing incorrect identification of artifacts from previous reinitializations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the storage system uses anchor pages to track allocated storage, then storage allocation can be maintained, but corrupted anchor pages cause inaccurate identification of the last allocated page leading to data overwriting or storage space orphaning

Engineering Contradiction:

Improveaccuracy of last allocated page identificationVSAvoidcorrupted anchor pages

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a timestamp as an intermediary element stored in superblocks and anchor pages. This timestamp serves as a mediator to verify the validity of anchor pages and identify the correct last allocated page, preventing corrupted anchor pages from causing data overwriting or storage space orphaning.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism by storing timestamps in superblocks and anchor pages, then using these timestamps to verify and correct the identification of the last allocated page. This feedback loop ensures that even if anchor pages are corrupted, the system can recover accurate information through the timestamp verification process.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If the storage system reinitializes, then storage can be reset and reused, but reinitialization can cause corrupted anchor pages to be misinterpreted as valid, leading to incorrect storage allocation

Engineering Contradiction:

Improvereinitialization capabilityVSAvoidaccuracy of storage allocation during recovery

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by storing timestamps in superblocks and anchor pages before reinitialization occurs. These pre-stored timestamps serve as reference markers that remain valid even after reinitialization, enabling the system to accurately identify the last allocated page during recovery without being misled by corrupted anchor pages.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The timestamp acts as an intermediary that bridges the gap between reinitialization and accurate storage allocation. By storing the timestamp before reinitialization and using it during recovery, the system can distinguish between valid and corrupted anchor pages, maintaining reliable storage allocation despite the reinitialization process.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the storage system scans all pages to find the last allocated page, then accurate identification can be achieved, but this increases recovery time and reduces performance

Engineering Contradiction:

Improveaccuracy of last allocated page identificationVSAvoidrecovery process time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent stores timestamps in anchor pages and superblocks as a preliminary action, so that during recovery the system can directly access this pre-computed information to identify the last allocated page without scanning all pages. This preliminary storage of timing information dramatically reduces recovery time while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a copy of the timestamp information in both anchor pages and superblocks. This copying allows the system to verify the validity of anchor pages through multiple sources (both the anchor page itself and the superblock), enabling accurate identification without requiring a full scan of all storage pages.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS11537300B2Identifying allocated blocks in a storage system

Publication Date: 2022.12.27 EMC IP HLDG CO LLC

AI summary

Techniques are used for identifying allocated blocks in a storage system. The techniques may be used to provide, among other things, retrieval of a value associated with a most recent reinitialization of the storage system. For a tier of user data storage in the storage system, a page of storage with the value and a marker indicating that the page marks an end of storage that has been allocated for the tier of user data storage may be identified. Storage may be allocated from a page immediately preceding the identified page.