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Method to mitigate data loss in a multiple failure scenario Disclosure Number: IPCOM000073582D
Original Publication Date: 2005-Feb-22
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 24K

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This disclosure provides a method to mitigate the data lost in a storage system during a multi-failure event which cause the loss of all copies of modified data in the storage systems cache.

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Method to mitigate data loss in a multiple failure scenario

Storage controllers often signal to the host computer that a disk write operation is completed and the data is stored to disk before the data is actually stored on the media. This hides the mechanical and other latencies of the actual storage devices (e.g. disks, flash memory or tape) from the host computer to give the appearance of faster response time. In signalling to the host that the write is completed, the storage system is in asserting that from the host computers perspective the data, the data has the same reliability characteristics as if it were on disk. This includes the persistence of the data through a power loss. The data that has been accepted by the storage controller but not stored on the actual device is often referred to as "modified data".

Storage controllers use several techniques to accomplish this, the most common being battery backing up the system in a manner that allows the system to write data that hasn't been written to the proper location on the storage devices to something that will preserve the data during the power loss. For example, the data and the necessary control information to identify the data, may be written to a special device such as flash memory or disk drive, written to the intended storage device or kept memory which remains functional because power is supplied by batteries. In highly available systems, multiple copies of the modified data are kept in independ...