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Multi-Target Storage Feature Establish Command For Copying

IP.com Disclosure Number: IPCOM000210829D
Publication Date: 2011-Sep-12
Document File: 3 page(s) / 20K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a new design for a storage device feature that allows a customer to create two or more copies of data with a single Establish command without stopping host input/output and without the lengthy wait for a physical copy to complete. The copies are immediately available at the conclusion of the logical copy. The method allows the user to specify one source volume and two or more target volumes.

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Multi-Target Storage Feature Establish Command For Copying

A popular storage device feature is one that allows users to very quickly create point in time copies of entire logical volumes or data sets. With copy services that use this feature, customers often request the ability to have multiple copies of source data while continuing to run to the source data. The multiple copies could then be used for backup, test operations, or other purposes of customer interest.

The feature's Establish command performs a 'logical' copy. It does not copy the data from the source to the target; it only creates the relationship between the source and the target. The command itself completes successfully once the logical copy has been created. A 'physical' copy may be done subsequent to the logical copy; the Establish command parameters indicate background copy. Once the logical copy has been created, a physical copy is done in the background.

The current art requires the customer to stop input/output (I/O) and issue multiple Establish commands to get multiple exact copies of data. The current feature's Establish command only allows one source and one target volume to be specified.

There is no single step solution with the current microcode. The solutions to obtain multiple exact copies of data with the storage device feature require multiple steps. There are two such multiple step solutions:
1. Requires the customer to stop host I/O to the source
A. The customer stops all I/O to source (A)
B. The feature's Establish command is issued with source (A) and target (B)
C. The feature issues a second Establish command with source (A) and target (C).

D. Once both commands complete after the logical copy is established from A->B and A->C, the customer can restart I/O to the source (A).

The problem with solution #1 is that the customer must stop their applications from running to the source (A) during the logical copies.

2. To avoid stopping I/O to the source volume, the storage feature uses two separate Establish commands
A. The customer stops all I/O to the first target (B).
B. The feature issues the Establish command with source (A) and target (B). This command is issued with background copy and non-persistent parameters. These parameters ensure a physical copy; upon completion of the physical copy, the target volume (B) is an exact copy of the source
(A), and the relationship is removed.
C. The feature then issues a second Establish command with source (B) and target (C). B->C can be done as simply a logical copy

The problem with solution #2 is that the customer must issue two Establish commands, and still needs to hold off I/O to volume B. The second target (C) is not a true (physical)

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copy unless there was background copy that completed.

With the disclosed new design, the customer is able to create two copies of data with a single storage feature Establish command without stopping host I/O and without the lengthy wait for a physical copy...