Shared File System Unmap Privilege Throttling for I/O Performance
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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 overwhelming the storage device, 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
1Productivity
If all hosts are allowed to issue unmap commands simultaneously to the shared file system, then storage space can be deallocated efficiently from all hosts, but the processing resources of the storage device become overwhelmed and performance of other commands degrades
Solution Approach 1:
The patent segments the unmap command processing by introducing unmap privilege slots that divide access rights among multiple hosts. Instead of allowing all hosts to issue unmap commands simultaneously, the system divides the storage device's processing capacity into discrete privilege slots, with each slot granted to one host at a time. This segmentation prevents resource overwhelming while maintaining efficient deallocation across multiple hosts through time-multiplexed access.
2Quantity of substance
If the number of hosts accessing the shared file system increases, then storage capacity utilization improves, but the likelihood of unmap commands overwhelming storage device resources increases
Solution Approach 1:
The patent introduces an intermediary unmap privilege management mechanism between multiple hosts and the storage device. This intermediary system, implemented through privilege slots and a management host, mediates unmap command issuance by controlling which host can issue unmap commands at any given time. This intermediary layer simplifies load management by providing a structured framework for handling unmap commands from numerous hosts without requiring complex real-time load balancing or resource arbitration.
3Productivity
If unmap commands are processed immediately upon receipt from any host, then storage space reclamation is maximized, but other commands experience performance degradation due to resource contention
Solution Approach 1:
The patent implements periodic action through time-multiplexed unmap privilege assignment. Instead of continuously processing unmap commands from all hosts simultaneously, the system periodically grants unmap privileges to different hosts in a rotating manner through the privilege slot mechanism. This periodic assignment ensures that storage space reclamation continues across all hosts over time while preventing resource contention that would degrade read and write command performance during any given period.
Data Source
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.