Nimble Storage, Inc.

Hewlett Packard Enterprise Development LP

Chunqi Han

Anil Nanduri

Murali Krishna Vishnumolakala

The failure of a storage unit in a storage array of a storage system may render the storage unit unresponsive to any requests. Any writes to the storage system that occur during the failure of the storage unit will not be reflected on the failed unit, rendering some of the failed unit's data stale. Assuming the failed unit's data is not corrupted but is just stale, a partial rebuild may be performed on the failed unit, selectively reconstructing only data that is needed to replace the stale data. Described herein are techniques for storing information that identifies the data that needs to be rebuilt. When the storage unit fails, the segment identifier associated with the last data segment written to the storage system may be stored. Upon the storage unit recovering, the storage system can rebuild only those data segments whose identifier is greater than the stored segment identifier.

Methods and systems for storing information that facilitates the reconstruction of at least some of the contents of a storage unit on a storage system

Described herein are techniques for storing data in a redundant manner on a plurality of storage units of a storage system. While all of the storage units are operating without failure, only error-correction blocks are stored on a first one of the storage units, while a combination of data blocks and error-correction blocks are stored on a second one of the storage units. Upon failure of the second storage unit, one or more data blocks and one or more error-correction blocks formerly stored on the second storage unit are reconstructed, and the one or more reconstructed data blocks and the one or more reconstructed error-correction blocks are stored on the first storage unit.

Methods and systems for rebuilding data subsequent to the failure of a storage unit

Described herein are techniques for cancelling I/O requests. Initially, virtual memory of an application is assigned to a first portion of memory. The application may issue a read request to an external device. The external device is instructed to record any response to the read request in the first portion of memory. The read request may be cancelled as follows. The virtual memory of the application may be re-assigned to a second portion of the memory. If and when the external device finishes processing the read request, the external device's response to the read request may still be saved in the first portion of memory, even though the read request has been cancelled. Such action of the external device would ordinarily corrupt the virtual memory of the application, but due to the memory re-assignment, no corruption of the virtual memory occurs. Similar techniques may be applied to cancel write requests.

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Pleasanton, CA, United States of America

Chunqi Han