Eccs, Inc.

Ibrix, Inc.

Mark Ish

Steven Orszag

Philip Eric Jackson

Federico Antonio Giovannetti

File system coherency of a file system, particularly for system blocks, may be maintained by (i) duplicating and verifying the (system) blocks, (ii) writing (system) blocks as a sequence of atomic commands so that at any given time, there is a valid (system) block on a physical storage device, and/or (iii) defining the file system directory data structure with directory blocks, each of the directory blocks having at least one of a directory entry and a pointer, where updates to the directory data structure are performed atomically.

Checking the validity of blocks and backup duplicates of blocks during block reads

A computer disk cache management method and apparatus which employs a least-recently-used with aging method to determine a best candidate for replacement as a result of a cache miss. A hash function takes as its input a block number and outputs a hash index into a hash table of pointers. Each pointer in the hash table points to a doubly-linked list of headers, with each header having a bit map wherein the bits contained in the map identify whether a particular block of data is contained within the cache. An ordered binary tree (heap) identifies candidates for replacement such that the best candidate for replacement is located at the root of the heap. After every access to a cache line, the heap is locally reorganized based upon a frequency of use and an age of the cache line, such that the least-frequently-used and/or oldest cache line is at the root of the heap.

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Shrewsbury, NJ, United States of America

Mark Ish