No data loss it disaster recovery over extended distances

This application is a continuation of and claims priority from U.S. patent application Ser. No. 11/534,546, entitled “NO DATA LOSS IT DISASTER RECOVERY OVER EXTENDED DISTANCES” filed on Sep. 22, 2006, which application claims priority from United States Provisional Application Ser. No. 60/722,369, entitled “NO DATA LOSS IT DISASTER RECOVERY OVER EXTENDED DISTANCES” filed on Sep. 30, 2005. The entire disclosures of the referenced applications are incorporated herein by reference.

The present invention relates generally to information technology systems, and more particularly to providing zero loss data protection and automated data recovery over extended distances.

In an information technology (IT) system, it is often desirable to replicate data stored at one location at another location so that if an event occurs (e.g., an equipment failure, a power failure, a natural disaster, or a terrorist attack or other man-made event) that damages or otherwise renders the data at the first location inaccessible, the data can be recovered from the second location. The first location may be referred to as the primary site, the second location may be referred to as the disaster recovery site, and such an occurrence may be referred to as a disaster event. In order to provide sufficient assurance that the disaster recovery site will not be effected by the disaster event effecting the primary site, the disaster recovery site must be geographically separated from the primary site by a sufficient distance.

When replicating the data at the disaster recovery site, it may be desirable to do so in a synchronous manner such that when data is created, updated or stored at the primary site, such data is replicated to the disaster recovery site first and only after receiving an acknowledgement from the disaster recovery site of successful replication is the data write considered complete and successful at the primary site. This allows for no lost data if the primary site goes down. However, excessive roundtrip packet delays resulting from long distances and other network conditions between the primary and disaster recovery sites prevents synchronous replication of data from the primary site to the disaster recovery site. This difficulty is present regardless of whether data replication takes place in the storage, middleware, or application layer of the IT system. Excessive roundtrip packet delays can be unacceptable since operation of applications creating, updating or accessing the data will be delayed while awaiting confirmation that the data has been replicated at the disaster recovery site.

Accordingly, the present invention introduces an intermediary site between the primary site and the disaster recovery site. The primary site may be referred to herein as the first site, the intermediary site may be referred to herein as the nearby safe site or the second site, and the disaster recovery site may be referred to herein as the third site. The data is replicated from the primary site to the nearby safe site and then subsequently replicated from the nearby safe site to the disaster recovery site. The nearby safe site may be geographically remote from the primary site such that the nearby safe site would be expected to survive a disaster event effecting the primary site for some period of time after the primary site goes down, but not necessarily survive indefinitely. However, the nearby safe site is located close enough to the primary site such that synchronous data replication is possible between the primary site and the nearby safe site without encountering unacceptable roundtrip packet delays. The disaster recovery site is located far enough from the primary site that the disaster recovery site would be expected to survive the disaster event effecting the primary site. Because the data has already been replicated to the nearby safe site, asynchronous replication of the data from the nearby safe site to the disaster recovery site is acceptable.

The nearby safe site includes a number of desirable characteristics. For example, the nearby safe site is close enough to the primary site that roundtrip packet delays between the nearby safe site and the primary site would not be detrimental to the user software applications. A typical maximum distance is, for example, one-hundred kilometers or even two-hundred kilometers, although actual allowable distances depend on the actual network paths traversed, roundtrip packet delays encountered, and the software application sensitivity to roundtrip packet delays. The nearby safe site can be run in a “lights out” configuration with no regular staffing requirements and is expected to operate in case of chemical, biological, or nuclear contamination. The primary hardware components at the nearby safe site are data storage devices as well as application servers. The data on the data storage devices could optionally be encrypted allowing the nearby site and its assets to be shared among multiple customers at different physical locations. The nearby site is physically protected to continue to operate for a relatively short period of time after the primary site has sustained a disaster, thereby allowing for the completion of the data transfer that has been buffered at this site to the disaster recovery site.

According to one aspect of the present invention, an extended distance data recovery system includes a first data storage device located at a first site, a second data storage device located at a second site, a third data storage device located at a third site, and a computer executable control process coordinating all three sites. The first data storage device has data stored thereon. The second data storage device is communicatively connected with the first data storage device, and the third data storage device is communicatively connected with the second data storage device. The computer executable control process is executable to direct synchronous replication of the data onto the second data storage device. The control process is also executable to direct asynchronous replication of the data from the second data storage device onto the third data storage device. The computer executable control process is executable to coordinate among the three sites the state of application servers, storage replication, network address changes, and other prerequisite aspects of the IT infrastructure required to allow the application servers to successfully start at the disaster recovery site.

According to another aspect of the present invention, a method for providing recovery of data and operational continuity of computer applications accessing the data if an event occurs effecting access to the data on an information technology system is provided includes the step of storing the data at a first site. The data is synchronously replicated from the first site to a second site under the direction of a computer executable control process. The data is asynchronously replicated from the second site onto a third site, also under the direction of the control process. The operational status of the first site is monitored, and, upon occurrence of the event, location identifying information associated with the data is updated so that computer applications access the data from the second site and/or the third site.

These and other aspects and advantages of the present invention will be apparent upon review of the following Detailed Description when taken in conjunction with the accompanying figures.

DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and further advantages thereof, reference is now made to the following Detailed Description, taken in conjunction with the drawings, in which:

FIG. 1 is block diagram showing one embodiment of an extended distance data recovery system and the operation thereof in accordance with the present invention;

FIG. 2 is block diagram showing another embodiment of an extended distance data recovery system and the operation thereof in accordance with the present invention; and

FIG. 3 is block diagram showing one more embodiment of an extended distance data recovery system and the operation thereof in accordance with the present invention.

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