Mainframe Storage Thin Provisioning Page Allocation
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Solution Overview
Problem
In mainframe storage systems using Thin Provisioning, actual pages are often used ineffectively due to the presence of non-zero data other than user data, making it difficult to identify and free up unnecessary pages without a high load on the system.
Innovation Solution
A storage control apparatus manages actual pages by identifying tracks without user records and canceling their allocation to virtual pages, using management information to synchronize this process with write commands, thereby preventing ineffective use of actual pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the zero pattern determination is applied to identify unnecessary actual pages in mainframe storage, then actual pages can be freed up, but the system load becomes too high and the approach becomes unrealistic
Solution Approach 1:
The patent applies preliminary action by maintaining management information that pre-records which tracks contain user records before any determination process. When a read command is received, the system checks this pre-prepared management information to quickly identify whether an actual page contains only non-user data, avoiding the need to perform zero pattern determination on the actual page data itself. This preliminary preparation of metadata enables fast identification of removable pages without loading the system with heavy data analysis.
2Reliability
If actual pages are allocated to virtual pages for copied user data, then data can be stored, but actual pages are used ineffectively when the copied data is not needed
Solution Approach 1:
The patent implements feedback by monitoring read commands and determining whether accessed virtual pages have corresponding allocated actual pages. When a read command is received for a virtual page without an allocated actual page, the system returns all-zero data, providing feedback information that can be used to identify patterns of unnecessary allocations. This feedback mechanism enables the system to learn which virtual pages consistently access only zero data and potentially release their allocated actual pages, improving effective storage utilization while maintaining data reliability.
Data Source
AI summary
Each actual page inside a pool is configured from a plurality of actual tracks, and each virtual page inside a virtual volume is configured from a plurality of virtual tracks. A storage control apparatus of a mainframe system has management information that includes information denoting a track in which there exists a user record, which is a record including user data (the data used by a host apparatus of a mainframe system). Based on the management information, a controller identifies an actual page that is configured only from tracks that do not comprise the user record, and cancels the allocation of the identified actual page to the virtual page.