Hewlett-packard Company

David M Jacobson

Robert M English

Chia-Chiang Chao

Alexander A Stepanov

Andrew J Wilkes

A method and apparatus for determining when all packets of a message sent over a computer network by a source computer have arrived at a destination computer includes a counter located at the source computer for storing an initial value and for assigning a delta value to each packet in the message, where the last packet stores a delta value that is equal to the counters initial value minus number of packets previously sent modulo the counter range; and includes an accumulator located at the destination computer for extracting the delta value from each packet of the message. The destination computer is notified that all packets in the message have arrived only when the sum of the extracted delta values stored in the accumulator is equal to zero modulo the capacity of the accumulator.

Method and apparatus for determining when all packets of a message have

An electronic data storage system including a memory, a plurality of magnetic disk units, and a controller. The memory contains an index cross-referencing logical address with physical addresses, an obsolete list and a free list. In response to a 'write ' command, the controller selects a physical address according to which segment can be used the most quickly, appends a tag to the data to be written, and writes the data to the selected segment. Appropriate entries are made in the index and the free list. The system recovers from memory loss by using a checkpoint log and a set of checkpoint segments on the disk that together contain backups of the index and other critical information needed to restore the system. Group indices are used for roll-back groups; operations on data in a group are invisible outside the group until after a 'commit ' command is issued.

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Santa Clara, CA, United States of America

David M Jacobson