Postponing Bitmap Transfers in Disk Array Trespass Operations

Solution Overview

Problem

Conventional systems experience lengthy delays and degraded I/O performance during LUN ownership migration due to the necessity of communicating delta maps and configuration information between storage processors, which is unnecessary and bandwidth-intensive, especially during trespass operations.

Innovation Solution

The method involves postponing bitmap transfers and eliminating configuration information transfers during trespass operations by maintaining change tracking data structures locally and calculating the image phase indicator from stored information, allowing the clone group to be associated with a new storage processor without transferring these data structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If delta maps and configuration information are transferred between storage processors during LUN ownership migration, then the migrating LUN can be accessed for I/O operations, but the transfer time is lengthy due to I/O bandwidth limitations, resulting in degraded I/O performance

Engineering Contradiction:

ImproveLUN ownership migration completenessVSAvoidtrespass time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary actions by maintaining change tracking data structures (delta maps) and configuration information locally in memory at each storage processor. When a trespass operation is initiated, the receiving SP already has the necessary data structures in its memory, eliminating the need for time-consuming transfers during the migration process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates and maintains local copies of change tracking data structures and configuration information at each storage processor. Instead of transferring these data structures during trespass operations, each SP maintains its own copy, allowing immediate access and eliminating transfer delays.

Inventive Principle:

Principle #26Copying

2Reliability

If delta maps and configuration information are transferred between storage processors during LUN ownership migration, then the migrating LUN can be accessed for I/O operations, but I/O bandwidth is consumed by the transfer process, resulting in degraded I/O performance

Engineering Contradiction:

ImproveLUN ownership migration completenessVSAvoidI/O performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs preliminary actions by maintaining change tracking data structures (delta maps) and configuration information locally in memory at each storage processor. When a trespass operation is initiated, the receiving SP already has the necessary data structures in its memory, eliminating the need for time-consuming transfers during the migration process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates and maintains local copies of change tracking data structures and configuration information at each storage processor. Instead of transferring these data structures during trespass operations, each SP maintains its own copy, allowing immediate access and eliminating transfer delays.

Inventive Principle:

Principle #26Copying

3Reliability

If configuration information is transferred during trespass operations, then synchronization processing activities can be tracked, but unnecessary bandwidth is consumed since much of the communication bandwidth is unnecessary

Engineering Contradiction:

Improvesynchronization processing trackingVSAvoidbandwidth consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system extracts and eliminates the unnecessary portion of the process by removing configuration information transfers entirely from the trespass operation. The patent demonstrates that configuration information transfers can be completely eliminated while maintaining full functionality, as the receiving SP can reconstruct or retrieve this information through alternative means.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system performs preliminary actions by maintaining change tracking data structures (delta maps) and configuration information locally in memory at each storage processor. When a trespass operation is initiated, the receiving SP already has the necessary data structures in its memory, eliminating the need for time-consuming transfers during the migration process.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7529887B1Methods, systems, and computer program products for postponing bitmap transfers and eliminating configuration information transfers during trespass operations in a disk array environment

Publication Date: 2009.05.05 EMC IP HLDG CO LLC

AI summary

Methods, systems, and computer program products for postponing bitmap transfers and eliminating configuration information transfers during trespass operations in a disk array environment are disclosed. According to one method, a clone group is stored on a disk array, the clone group including a logical unit (LUN) representing a storage partition on the disk array and a clone of the LUN, the clone being a copy of the data referenced by the LUN. The clone group is associated with a first storage processor (SP) for writing data to the disk array. Changes between the LUN and the clone are tracked by maintaining a data structure indicative of the changes in a memory associated with the first SP. The association of the clone group is changed to a second SP for writing data to the disk array without transferring the data structure to memory associated with the second SP.