Importance

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Abstract

An array controller of a log structured array dynamically defines segments as data is taken from a write buffer and recorded into disk storage units of the log structured array such that a segment includes blocks selected from the various disk storage units at the time of segment definition so as to minimize disk arm travel. Each time a segment from the write buffer must be written to disk, the new disk segment is defined in response to current disk arm position for each disk platter in a disk storage unit. The array controller maintains a segment definition table that indicates the disk storage unit locations corresponding to each segment. In addition, garbage collection of used blocks is performed in response to disk arm idle time such that garbage collection is not performed only when there are too few empty segments. Rather, garbage collection is performed when a disk arm has been idle for a predetermined time. A variety of garbage collection schemes are described.

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First Claim