System and method for reconstructing lost data in a storage system

Abstract

A system (and method) for determining reconstruction formulas for partial strip reconstruction in a storage system in which a plurality of lost strips have been detected, includes using a combination of a direct reconstruction method and a sequential reconstruction method.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application is related to U.S. patent application Ser. No. 10 / 978,389, filed on Nov. 2, 2004, to Hafner et al., entitled “SYSTEM AND METHOD FOR RECOVERY OF DATA FOR A LOST SECTOR IN A STORAGE SYSTEM” having IBM Docket No. YOR920040318US1, assigned to the present assignee and which is incorporated herein by reference, in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to a system and method for determining reconstruction formulas for reconstruction of lost data in a storage system, and more particularly, to a system and method for determining reconstruction formulas for partial strip reconstruction including a combination of a direct reconstruction method and a sequential reconstruction method. [0004] 2. Description of the Related Art [0005] Generally, erasure codes (e.g., RAID schemes) are fundamental tools for providing data reliability in storage syste...

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Benefits of technology

[0016] According to the exemplary aspects of the present invention, from an input set of data elements to reconstruct, the exemplary method can identify at least one data element which has a lowest reconstruction cost using the direct reconstruction method, reconstruct the data element using the direct reconstruction method, and remove the data element from the input set of data elements to reconstruct.

[0017] On the other hand, from the input set of data elements to reconstruct, another exemplary method can determine if at least one data element from the input set is sequentially reconstructable by no more than (i.e., equal to or less than) a predetermined number of steps of the sequential method using available data and parity elements, can reconstruct the data element using the sequential reconstruction method, and can remove the data element from the input set of data elements to reconstruct.

[0018] If at least one data element from the input set is not sequentially reconstructed by no more than (i.

Problems solved by technology

However, this is very complicated and typically requires either additional special purpose hardware or complicated and expensive software.

The published literature generally does not provide algorithms for recovering partial disk data.

However, there are scenarios where partial lost data needs to be recovered, but not all the lost data is required.

Because the typical reconstruction algorithms are sequential in nature and are designed to recover all the lost data, they may not be the most cost effective approaches to reconstruction of partial strips.

For example, when the required partial disk data elemen

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