Online Cache State Transition in Storage Arrays
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Solution Overview
Problem
Existing storage systems face challenges in managing cache storage efficiently, particularly in transitioning between cache enabled and disabled states without disrupting data flow and ordering, especially when storage arrays are taken offline or shut down, leading to losses in time and money.
Innovation Solution
A primary storage array can switch between cache enabled and disabled states online, using asynchronous storage to transition from multiple gigabyte FIFO write caches to a synchronous single cache write slot, allowing for seamless data flow and ordering without shutting down applications or reconnecting storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If storage arrays are taken offline or shut down to disable cache, then cache can be disabled, but data flow and data ordering are disrupted and applications must be shutdown
Solution Approach 1:
The system dynamically transitions cache operations from asynchronous to synchronous mode while online, allowing the storage array to adapt its caching behavior without shutdown. The cache is progressively disabled by increasing host delays until data flows synchronously, maintaining data availability while eliminating the need for offline operations.
Solution Approach 2:
The invention changes the operational parameters of the cache by progressively increasing host delays and transitioning from asynchronous to synchronous data flow. This parameter adjustment allows the cache to be disabled while the system remains online, avoiding disruption to data flow and application operations.
2Reliability
If cache is disabled by shutting down storage arrays, then cache storage is disabled, but time and money are lost due to downtime
Solution Approach 1:
The system performs preliminary actions by progressively increasing host delays and transitioning cache operations to synchronous mode before completely disabling the cache. This gradual transition ensures data flows synchronously to the subordinate array before cache is fully disabled, eliminating downtime while achieving cache disablement.
Solution Approach 2:
The invention maintains continuous data flow throughout the cache disablement process by transitioning from asynchronous to synchronous operations online. The useful action of data storage continues uninterrupted while the cache is progressively disabled, preventing any loss of time or operational downtime.
3Productivity
If asynchronous FIFO write cache is used, then data flow is buffered, but transitioning to synchronous cache disrupts data ordering and requires offline operation
Solution Approach 1:
The system dynamically adjusts the data flow mode from asynchronous FIFO buffering to synchronous ordering by progressively increasing host delays. This dynamic transition maintains data ordering stability while adapting the buffering behavior, allowing the system to move from high-performance asynchronous mode to ordered synchronous mode without offline operation.
4Reliability
If storage arrays are disconnected and reconnected to disable cache, then cache is disabled, but LUNs must be re-mapped and data flow disrupted
Solution Approach 1:
The invention uses host delays as an intermediary mechanism to transition cache operations from asynchronous to synchronous mode. This intermediary approach allows cache disablement without physical disconnection or LUN re-mapping, eliminating complex reconfiguration operations while achieving the desired cache configuration change.
Data Source
AI summary
Embodiments include methods, apparatus, and systems for enabling and disabling cache in storage systems. One embodiment includes a method that changes a time period for delaying host requests received at a cache of a storage device and converts the storage device from a cache enabled state to a cache disabled state while the storage device is online.