International Business Machines Corporation

Terrence James Stewart

Sheldon Bernard Levenstein

Michael Joseph Corrigan

Francis Daniel Lawlor

Brian Eldridge Clark

George D Timms, Jr

Werner E Schmidt-Stumpf

It is known that virtual memory segments that are allocated together tend to be used together. With existing sequential address allocation mechanisms, this in turn means that programs tend to end up using the same set or sets of virtual segment addresses (i.e., in the same minitable or minitables), which, as mentioned, leads to increased address translation time because of clumping. The address allocation mechanism of the present invention reduces clumping by allocating virtual segment addresses in a pseudo-random order. This decreases the likelihood that virtual segment addresses that are allocated together end up in the same set or sets of virtual segment addresses within the address translation table.

Pseudo-random address generation mechanism that reduces address

A storage management mechanism distributes parity blocks corresponding to multiple data blocks substantially equally among a set of storage devices. N storage units in a set are divided into a multiple of equally sized address blocks, each containing a plurality of records. Blocks from each storage unit having the same address ranges form a stripe of blocks. Each stripe has a block on one storage device containing parity for the remaining blocks of the stripe. Further stripes also have parity blocks, which are distributed on different storage units. Parity updating activity associated with every change to a data record is therefore distributed over the different storage units, enhancing access characteristics of the set of storage devices. The parity updating activity also includes the use of an independent version number stored with each data record and corresponding version numbers stored with the parity record. Each time a data record is changed, its version number is incremented and the corresponding version number in the parity record is incremented with the parity record update.

Parity spreading to enhance storage access

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Rochester, MN, United States of America

Terrence James Stewart