Browse Prior Art Database

I/O Priority Management for Copy Services Relationships

IP.com Disclosure Number: IPCOM000198983D
Publication Date: 2010-Aug-19
Document File: 4 page(s) / 36K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention consists of a method and procedure for handling customer specified priorities on I/O tasks originating from copy service operations including point in time copy (Flash Copy), synchronous copy (Metro Mirror), asynchronous copy (Global Copy), and consistent asynchronous copy (Global Mirror).

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I/O Priority Management for Copy Services Relationships

Currently, there are ways of ensuring certain host I/O tasks do not starve out other important host I/O tasks on the storage server. One known tool can throttle certain host I/O activities when they are constrained on a given resource, such as a Rank, Device Adaptor, or Host Adaptor. This throttling allows the storage server to give priority to host I/O that has been identified as more important by a user.

There are more ways to generate I/O on the storage server than purely host initiated I/O. The next major I/O source on the storage server comes from copy services operations. These copy services operations, such as point in time copy (Flash Copy), synchronous copy (Metro Mirror), asynchronous copy (Global Copy), and consistent asynchronous copy (Global Mirror).

Today, a customer can not differentiate the priority of the host I/O done to a given volume and the subsequent copy services I/O generated.

This would be beneficial in the following example cases:

A temp volume must have high host I/O performance as not to impact

applications, but its backup is not as important as other more business critical volumes. Thus the consistency group formation of this volume should be set lower than its host I/O priority.
A point in time copy of 6000+ volumes is done each night with background copy.

The customer finds that the background copy always completes ahead of time, but host I/O on a different set of critical volumes is greatly impacted while this backup occurs. Further investigation shows this is due to stress on the target rank being used by the point in time copy. The point in time copy can thus be created at a lower priority as not to interfere with the remaining host I/O during this period.
The customer has critical audit requirements which are not being met for

ensuring consistency groups for consistent asynchronous copy relationships on certain volumes complete within a given recovery point objective. The customer can increase the priority of the consistent asynchronous copy session. Thus any I/O coming from this session will be prioritized on any given resource where contention occurs.

This invention consists of a method and procedure for handling customer specified priorities on I/O tasks originating from copy service operations including point in time copy (Flash Copy), synchronous copy (Metro Mirror), asynchronous copy (Global Copy), and consistent asynchronous copy (Global Mirror).

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I/O Priority Manager Today

Currently, customers are able to set volume priorities via the DS Command Line Interface (DSCLI) when a volume is created or modified after a volume is created.

Example:

# Define performance group #4
dscli> mkperfgrp -policy XYZ PG4

# Assign volumes to performance group #4
dscli> chfbvol
-

G4

After the volume is modified, it will use algorithm XYZ in order to achieve high priority I/O rates to this volume. The algorithm specified includes metri...