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A Method and System for Minimizing Time for Switching between Synchronous and Asynchronous Mirroring of Storage Devices

IP.com Disclosure Number: IPCOM000235025D
Publication Date: 2014-Feb-25
Document File: 2 page(s) / 63K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system is disclosed for minimizing time required for switching between a synchronous mode and an asynchronous mode of creating mirrors for one or more storage devices comprised in a consistency group, using an Input/ Output (I/O) pause command.

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A Method and System for Minimizing Time for Switching between Synchronous and Asynchronous Mirroring of Storage Devices

Currently, businesses are looking for solutions that enable switching between a synchronous and an asynchronous mode for mirroring storage devices. For instance, during slow periods, businesses may choose to switch from the synchronous mode to the asynchronous mode. Businesses may choose the vice versa of switching to the synchronous mode during peak hours because of latency issues inherent to the asynchronous mode.

In certain situations, the infrastructure for creating the copy using the synchronous mode is different from the infrastructure for the asynchronous mode. In such situations, switching between the modes involves incurring an overhead in terms of a time required for the switching. For instance in a technique known as offline initialization for switching, the overhead is incurred during an initialization phase of the technique. In the initialization phase, changes made to the storage device at the primary site are identified by comparing hashes of data stored in the primary site with, hashes stored in the secondary site. As such comparison

of hashes requires time if there is a failure at the primary site, some changes made at the primary site may not be propagated in time to the secondary site. There is a need therefore for eliminating the initialization phase in order to minimize the time required for switching between the synchronous mode and the asynchronous mode.

Disclosed is a method and system for minimizing time required for switching between a synchronous mode and an asynchronous mode of mirroring one or more storage devices comprised in a consistency group, using an Input/ Output (I/O) pause command.

The method and system uses the I/O pause command for pausing all writes to one storage device of the consistency group, at a time. Thereafter, the method and system deactivates a current mode of creating mirrors. The current mode can either be the synchronous mode, or the asynchronous mode. In one embodiment wherein the current mode is the asynchronous mode, the method and system creates a mirrored snapshot of the storage device subsequent to deactivating the asynchronous mode.

Thereafter, the method and system deletes a mirror for the storage device created using the current mode. Similarly, all residual snapshots created for storing changes to the storage device, are also deleted. Alternatively, th...