Shared File System Unmap Privilege Transfer to Prevent Command Overload
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Solution Overview
Problem
The processing resources of storage devices managing shared file systems are overwhelmed by numerous unmap commands from multiple hosts, leading to degraded performance of other commands such as read and write operations.
Innovation Solution
Implementing a mechanism to manage unmap privileges, where only hosts with the unmap privilege can issue unmap commands, and throttling the issuance of these commands to prevent resource overload, using methods such as scanning unmap privilege files, transferring privileges between idle hosts, or capping the rate and amount of storage space deallocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hosts are allowed to issue unmap commands freely to deallocate storage space, then storage space management flexibility is improved, but storage device processing resources become overwhelmed
Solution Approach 1:
The patent introduces an unmap privilege mechanism as an intermediary control layer between hosts and storage device. A privilege file tracks which hosts have unmap privileges, and the storage device mediates unmap commands by checking this file. This intermediary system allows flexible storage management while preventing resource overload by controlling which hosts can issue unmap commands and at what rate.
2Productivity
If multiple hosts simultaneously issue unmap commands to multiple LUNs, then storage utilization efficiency is improved, but command processing performance degrades
Solution Approach 1:
The patent implements periodic action by requiring hosts to wait for privilege availability before issuing unmap commands. The storage device periodically updates the privilege file and hosts periodically check for privilege availability. This periodic control mechanism allows multiple hosts to access multiple LUNs efficiently while preventing simultaneous command bursts that would degrade processing performance.
3Speed
If unmap commands are processed immediately upon receipt, then storage space deallocation speed is improved, but other command performance deteriorates
Solution Approach 1:
The patent applies partial action by allowing only a limited number of hosts to issue unmap commands at any given time, rather than allowing all hosts to do so simultaneously. The privilege mechanism restricts unmap command issuance to a subset of hosts, ensuring that storage device resources are not completely consumed by unmap operations, thus preserving performance for read and write commands while still achieving storage space deallocation.
Data Source
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AI summary
A host computer is configured to issue one or more unmap commands to a file system of a storage device, the file system being shared by a plurality of host computers including the host computer, by performing the steps of: acquiring unmap privilege information from the storage device, the unmap privilege information indicating whether or not an unmap privilege is available to the host computer; in response to determining that the unmap privilege is available, transmitting a request to update an unmap privilege file stored in the storage device to indicate that the host computer has the unmap privilege; and then issuing to the file system, the one or more unmap commands to deallocate storage space from one or more files of the file system.