System and method for recovering a segment directory for a log structured array

A data storage system for storing electronic data for a data processing system, the data storage system comprising:

• an array of storage devices, including a processor and memory, having a plurality of data blocks, designated as old data blocks and current data blocks, organized on the storage devices in segments striped across the storage devices;
• a main directory, stored in memory, containing the location on the storage devices of each of the current data blocks;
• a plurality of segment directories, each segment directory having information on the data blocks in a given segment;
• a checkpoint of the main directory written to the storage devices periodically and also written when a damaged segment directory is detected;
• and
• a list identifying damaged segment directories, wherein segment directories on the damaged segment directories list are rebuilt using information in the main directory and wherein segments listed in the damaged segment directories list do not participate in space reclamation procedures.

In a data storage system comprising an array of storage devices, including a processor and memory, having a plurality of data blocks organized on the storage devices in segments striped across the storage devices, and each segment including parity information used to reconstruct the data blocks of the segment in the event a storage device is damaged, wherein when a data block in a segment stored on the storage devices in a first location is updated, the updated data block is written as part of a different segment to a new storage location, and is designated a current data block, and the data block in the first location is designated an old data block, and having a main directory, stored in memory, that keeps track of the location on the storage devices of each of the current data blocks, a system for recovering a segment directory that is stored with a segment, having information on the data blocks in the segment, in the event the segment directory is damaged, comprising:

• means for maintaining a list identifying damaged segment directories;
• means for periodically writing the main directory to the storage devices;
• means for writing the main directory to the storage devices when a damaged segment directory is detected;
• and
• means for identifying current data blocks stored in each segment on the damaged segment directories list, and reconstructing a segment directory entry for each identified data block, during a procedure for reconstructing a damaged main directory.

An article of manufacture for use in storing and managing a plurality of sets of data blocks in a computer system having a processor, memory and a group of storage devices, wherein each set of data blocks is stored in a segment striped across the group of storage devices, the article of manufacture having a computer program code embodied in said medium which causes the computer system to:

• update a data block in a segment stored on the storage devices in a first location by writing the updated data block as part of a different segment to a new storage location, wherein the updated data block is designated a current data block, and the data block in the first location is designated an old data block;
• maintain a main directory, stored in memory, that keeps track of the location on the storage devices of each current data block;
• store on the storage devices, for each segment, a segment directory having information on the data blocks in the segment;
• write the main directory to the storage devices at periodic intervals for use in a main directory recovery procedure;
• write the main directory to the storage devices when a damaged segment directory is detected;
• maintain a list identifying damaged segment directories;
• and
• reconstruct the damaged segment directories on the list of damaged segment directories using the information in the main directory.