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Executing storage management tasks in a distributed storage system

IP.com Disclosure Number: IPCOM000171113D
Original Publication Date: 2008-May-29
Included in the Prior Art Database: 2008-May-29
Document File: 1 page(s) / 32K

Publishing Venue

IBM

Abstract

One of the important functions of the self-management component of Kybos is to ensure that system invariants are adhered to at all times. When the state of the Kybos system changes due to addition, change, or failure of resources, one or more invariants may be violated. Such violations are detected by the selfmanagement component of Kybos and appropriate remedial action is triggered. This remedial action is accomplished by spawned tasks that do whatever is necessary to make the invariants valid once again. Tasks have assigned priorities which are derived from the priority of the invariant they seek to fix. During execution , tasks use the resources of the Management Reserve resource pool. The management task scheduler (MTS) is responsible for correctly and efficiently scheduling tasks in a Kybos system. After tasks are created, they are submitted to the scheduler. The scheduler determines the appropriate time to execute the task based on the task’s priority, and state of the system and that of the other tasks. The goal of the scheduler is to execute the tasks as soon as possible while ensuring that the higher priority tasks are given preference over the lower priority ones. The purpose of this document is to discuss the following: Motivation for non-trivial task scheduling Task Model Design of the management task scheduler Task scheduling algorithms This work is in the context of our ongoing investigation into self-management for the Kybos distributed object storage system.

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THIS COPY WAS MADE FROM AN INTERNAL IBM DOCUMENT AND NOT FROM THE PUBLISHED BOOK

ARC820040237 Marc D McSwain/Almaden/IBM
Omer Zaki, Richard Golding, Guillermo Alvarez, Theodore Wong

Executing storage management tasks in a distributed storage system

When system invariants are violated, a Kybos system is made vulnerable to data or performance loss. The purpose of tasks is to make the system less vulnerable. The high-level purpose of the management task scheduler is to execute the tasks so that the window of vulnerability is minimized. The management task scheduler serves its purpose by doing the following:

Starting the execution of tasks only after the task is given all the resources it requires.

Starting the execution of tasks with higher priority before starting the tasks with lower priority.

Scheduling task execution such that all tasks are completed as fast as possible subject to resource and priority constraints. In trying to execute tasks as fast as is possible we believe that intelligent scheduling of tasks is warranted. For instance, in the scenario in which there is heavy contention between tasks the difference between a naïve task schedule and one that carefully orders tasks to use the resources more efficiently while honoring priorities, is significant.

Scheduling task execution such that tasks are started within reasonable time from w...