LUN Lock Transition Delay for Data Integrity
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Solution Overview
Problem
In high-availability data arrays, there is a challenge in determining which host, active or passive, controls a particular LUN, leading to potential issues during transitions and data integrity concerns.
Innovation Solution
A method where a lock for a LUN is initially defined as belonging to an active host, and if a write request from a passive host is received, it is delayed for a defined period to allow the active host to contest the transition. If the active host does not contest, the lock is transferred to the passive host, and if it does, the LUN and both hosts are placed into degrade mode to prevent data corruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the lock is immediately transferred to Host B upon receiving a write request, then the system responsiveness is improved, but data integrity may be compromised due to potential corruption during host transitions
Solution Approach 1:
The patent implements a delay period before transferring the lock from Host A to Host B. During this delay, Host A is given an opportunity to contest the transition by sending a contest message. This preliminary action allows the system to check for potential failures or data integrity issues before completing the host transition, thus preventing data corruption while still enabling relatively fast failover.
2Reliability
If the active host is given time to contest the lock transition, then data integrity is improved, but the system responsiveness deteriorates due to the delay in processing write requests
Solution Approach 1:
The patent implements a contest period that is longer than strictly necessary for data integrity protection. This excessive action ensures that even in edge cases with network latency or processing delays, the active host will have sufficient time to contest an unauthorized lock transition. The extended contest period prioritizes absolute data integrity over minimal responsiveness, accepting a longer delay as a conservative safety measure.
Data Source
AI summary
A method, computer program product, and computing system for receiving a reservation for a LUN from Host A, wherein the LUN is defined within a data array. A lock for the LUN is defined as Host A. A write request is received for the LUN from Host B. The lock for the LUN is defined as Transitioning A to B. The write request is delayed for a defined period of time.