System and method for on-line, real time, data migration

Abstract

A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table. When not busy servicing other requests, the replacement storage device operates in a background mode to migrate data elements so the data migration can occur concurrently with and transparently to system operations.

Description

[0001] This is a continuation-in-part of co-pending application for U.S. Pat. Ser. No. 08 / 522,903 filed Sep. 1, 1995 for a System and Method for On-Line, Real Time, Data Migration.[0002] 1. Field of the Invention[0003] This invention relates to data storage systems and more particularly, to a system and method for on-line replacement of an existing data storage subsystem.[0004] 2. Description of Related Art[0005] Data processing centers of businesses and organizations such as banks, airlines and insurance companies, for example, rely almost exclusively on their ability to access and process large amounts of data stored on a data storage device. Data and other information which is typically stored on one or more data storage devices which form part of a larger data storage system is commonly referred to as a database.[0006] Databases are nearly always "open" and constantly "in use" and being accessed by a coupled data processing system, central processing unit (CPU) or host mainframe...

AI Technical Summary

Problems solved by technology

The inability to access data is disastrous if not a crisis for such business and organizations and will typically result in the business or organization being forced to temporarily cease operation.

If the conversion takes more than two days or if the business or organization cannot withstand two days of inoperability, the need and desire to upgrade their data storage system may oppose an insurmountable problem.

Additionally, even on such prior art data storage systems, migrating data as a "background" task while the database is "open" does not take into account the fact that the data is constantly changing as it is accessed by the host or central processing unit and accordingly, if the old system is left connected to the host, there will always be a disparity between the data which is stored on the old data storage system and the data which has been migrated onto the new data storage system.

In such cases, the new data storage system may never fully "catch up" and be able to be completely synchronized to the old data storage system.

Images