A method is disclosed for maintaining consistent states of a file system. The file system progresses from one self-consistent state to another self-consistent state. The set of self-consistent blocks on disk that is rooted by a root inode is referred to as a consistency point. The root inode is stored in a file system information structure. To implement consistency points, new data is written to unallocated blocks on disk. A new consistency point occurs when the file system information structure is updated by writing a new root inode into it. Thus, as long as the root inode is not updated, the state of the file system represented on disk does not change. The method also creates snapshots that are user-accessible read-only copies of the file system. A snapshot uses no disk space when it is initially created. It is designed so that many different snapshots can be created for the same file system. Unlike prior art file systems that create a done by duplicating an entire inode file and all indirect blocks, the method of the present invention duplicates only the inode that describes the inode file. A multi-bit free-block map file is used to prevent data referenced by snapshots from being overwritten on disk.

Method for maintaining consistent states of a file system and for creating user-accessible read-only copies of a file system

Dynamic memory allocation has been a fundamental part of most computer systems since roughly 1960, and memory allocation is widely considered to be either a solved problem or an insoluble one. In this survey, we describe a variety of memory allocator designs and point out issues relevant to their design and evaluation. We then chronologically survey most of the literature on allocators between 1961 and 1995. (Scores of papers are discussed, in varying detail, and over 150 references are given.)

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Dynamic Storage Allocation: A Survey and Critical Review

A storage router and method for providing virtual local storage on remote storage devices to devices are provided. Devices are connected to a first transport medium, and a plurality of storage devices are connected to a second transport medium. In one embodiment, the storage router maintains a map to allocate storage space on the remote storage devices to devices connected to the first transport medium by associating representations of the devices connected to the first transport medium with representations of storage space on the remote storage devices, wherein each representation of a device connected to the first transport medium is associated with one or more representations of storage space on the remote storage devices and controls access from the devices connected to the first transport medium to the storage space on the remote storage devices in accordance with the map and using native low level block protocol.

Storage router and method for providing virtual local storage

A computer file system, having a multiplicity of distinct disk storage devices, includes a multiplicity of file directories, stored on various disks. Each file directory is used to translate file names into corresponding tag values. For each disk there is a file descriptor table with a file descriptor entry for every file stored on the disk. A single tag directory contains one tag entry for every file stored in the system. The tag directory is used by the file system to find a file by translating a tag value into a pointer to the disk on which the file is stored and a pointer to the file's file descriptor entry. To move a file from a first disk to a second disk, the file is copied to the second disk, a new file descriptor entry for the copied file is generated in the file descriptor table for the second disk, the copy of the file on the first disk is de-allocated, and the tag entry for the file is updated to point to the second disk and to the file's new file descriptor entry. Thus, a file can be moved from a first disk a second without having to locate and update all the corresponding file directory entries. In a preferred embodiment, the file system includes a routine that monitors disk loading and unused disk capacity. It determines when disk usage is imbalanced and automatically moves files among the disks so as to better balance disk usage.

System of device independent file directories using a tag between the directories and file descriptors that migrate with the files

An access system provides identity management and/or access management services for a network. An application program interface for the access system enables an application without a web agent front end to read and use contents of an existing encrypted cookie to bypass authentication and proceed to authorization. A web agent is a component (usually software, but can be hardware or a combination of hardware and software) that plugs into (or otherwise integrates with) a web server (or equivalent) in order to participate in providing access services.

Access system interface

A conditional broadcast or notification facility of a global lock manager is utilized to both serialize access to pages stored in local caches of counterpart processors in a distributed system and to ensure consistency among pages common to the caches Exclusive use locks are obtained in advance of all write operations When a page is to be updated, which page is cached in a processor other than that of the requester, then a delay is posed to the grant of the exclusive lock, all shared use lock holders to the same page notified, local copies are invalidated, exclusive lock granted, page is updated and written through cache, after which the lock is demoted to shared use

Multiprocessor system includes operating system for notifying only those cache managers who are holders of shared locks on a designated page by global lock manager

A computer-implemented method for the name-oriented accessing of files having at least zero records, any access path to files and records through an external store coupling the computer being defined by a pair of related directories. A first directory of record entries is sorted on a two-part token. The token consists of a unique sequence number assigned to the record and the sequence number of any parent record entry. Each record entry includes the token, file or record name, and external store address or pointer A traverse through the tokens constitutes a leaf-searchable B-tree. Rapid access to target records is by way of a name-sorted, inverted directory of names and tokens as a subset and which is reconstitutable from the first directory in the event of unavailability.

Method for dynamically expanding and rapidly accessing file directories

A method for managing space re-use with respect to the indices (nodes) of shadow written tree organized dynamic random accessed files/records/pages located in the external store of a CPU. The method reserves space in all non-leaf nodes and maintains a list of available node addresses. When a new node is required then space, if available, is obtained from the parent node list. Only when the parent list becomes exhausted is space (node) obtained from a node inventory manager. Deletion of a node causes its address to be placed on the free or available list maintained by that node's parent. If there is no space, then space on the parent node list is obtained by returning to the inventory manager that node on the list having the least locality with the existing subordinate (children) nodes of the parent.

Managing locality in space reuse in a shadow written B-tree via interior node free space list

A method for allowing weak-searchers of a B+-tree avoid locks that serialize access to the B+-tree structure The update technique used to achieve this ensures that the B+-tree is always in a correct state on secondary storage so that repair is not necessary after a system failure The assumption is made that the readers will complete their reading within a specified period but sometimes will need to be restarted because they have not completed their reading within a predetermined time period

Method for allowing weak searchers to access pointer-connected data structures without locking

A data cache in a computer operating system that dynamically adapts its size in response to competing demands for processor storage, and exploits the storage cooperatively with other operating system components An arbiter is used to determine the appropriate size of the cache based upon competing demands for memory The arbiter is entered cyclically and samples user's wait states The arbiter then makes a decision to decrease or increase the size of the cache in accordance with predetermined parameters

Gerald Parks Bozman

Papers

Multiprocessor system includes operating system for notifying only those cache managers who are holders of shared locks on a designated page by global lock manager

Method for dynamically expanding and rapidly accessing file directories

Managing locality in space reuse in a shadow written B-tree via interior node free space list

Method for allowing weak searchers to access pointer-connected data structures without locking

Arbitral dynamic cache using processor storage