Reservation Entity for Thin Provisioning Space
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Solution Overview
Problem
Existing thin provisioning systems face inefficiencies due to the need for pre-allocating storage space, which reduces the 'thinness' property and leads to storage space inefficiencies, as they reserve space ahead of time for specific thin devices, potentially resulting in underutilization of available storage capacity.
Innovation Solution
A method and system that utilize a reservation entity to manage storage space allocation in a thin provisioning environment, allowing for space reservation and allocation based on demand, using reserved space from a shared pool without pre-allocation, and communicating with multiple device reserved lists across storage pools to ensure space availability when needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space is pre-allocated when a thin device is bound to a storage pool, then sufficient allocated space is guaranteed to be available when needed, but storage space inefficiencies occur because the allocated space is held in reserve and reduces the thinness property
Solution Approach 1:
The system performs preliminary space reservation without immediate physical allocation. When a thin device is bound to a storage pool, the system reserves logical space entitlements in advance (creating reservation records in device reserved lists and pool reserved containers) but does not physically allocate the actual storage blocks until needed. This preliminary reservation action guarantees future space availability while avoiding the waste of holding space in reserve, as the space remains available for other uses until the thin device actually consumes it.
Solution Approach 2:
The invention introduces a reservation entity as an intermediary between the thin device and the physical storage pool. This reservation entity (comprising device reserved lists, pool reserved containers, and subscription information) acts as a mediator that tracks and manages space entitlements without directly occupying physical storage blocks. The intermediary reservation mechanism allows the system to guarantee space allocation policy compliance while maintaining the thin provisioning benefit of not pre-allocating actual storage capacity.
2Reliability
If space is pre-allocated for thin devices, then space availability is ensured, but the thinness property is reduced and storage resources are underutilized
Solution Approach 1:
The system implements dynamic space allocation where the amount of physically allocated storage to thin devices changes over time based on actual usage needs. Initially, when thin devices are bound to storage pools, only logical reservations are created without physical allocation. As thin devices consume data, space is dynamically allocated from the storage pool according to the subscription information and allocation policies. This dynamic approach maintains the thinness property by allowing storage resources to be adaptively reassigned to different devices based on real-time demands.
Solution Approach 2:
The invention changes the parameter of space allocation from a static pre-allocated state to a dynamic on-demand state. The system uses subscription information (including subscribed reserved track groups counters) to track entitled space, but the actual physical allocation parameter changes over time based on consumption. This parameter change allows the system to guarantee space availability through logical reservations while maintaining adaptability by physically allocating storage only when needed, thus preserving the thin provisioning characteristic.
3Ease of manufacture
If space is reserved ahead of time for specific thin devices, then allocation is simplified, but storage capacity utilization is reduced
Solution Approach 1:
The system creates a logical copy or representation of space entitlements through reservation records rather than physically duplicating actual storage blocks. When space is reserved for a thin device, the system creates subscription information and reservation records (copies of space entitlements) that track the reserved capacity without consuming physical storage resources. This copying approach simplifies allocation management by providing clear tracking of entitled space while maintaining full utilization of available storage capacity, as the actual blocks remain unallocated until needed.
Data Source
AI summary
Guaranteeing space availability for thin devices includes reserving space without committing, or fully pre-allocating, the space to specific thin device ranges. Space may be held in reserve for a particular set of thin devices and consumed as needed by those thin devices. The system guards user-critical devices from running out of space, for example due to a “rogue device” scenario in which one device allocates an excessive amount of space. The system uses a reservation entity, to which a thin device may subscribe, which reserves space for the thin device without allocating that space before it is need to service an I/O request.