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Showing papers on "Server published in 1995"


Proceedings ArticleDOI
03 Dec 1995
TL;DR: Bayou as discussed by the authors is a replicated, weakly consistent storage system designed for a mobile computing environment that includes portable machines with less than ideal network connectivity, and it includes novel methods for conflict detection, called dependency checks, and per-write conflict resolution based on client-provid ed merge procedures.
Abstract: Bayou is a replicated, weakly consistent storage system designed for a mobile computing environment that includes portable machines with less than ideal network connectivity. To maximize availability, users can read and write any accessible replica. Bayou’s design has focused on supporting application-specific mechanisms to detect and resolve the update conflicts that naturally arise in such a system, ensuring that replicas move towards eventual consistency, and defining a protocol by which the resolution of update conflicts stabilizes. It includes novel methods for conflict detection, called dependency checks, and per -write conflict resolution based on client-provid ed mer ge procedures. To guarantee eventual consistency, Bayou servers must be able to rollback the effects of previously executed writes and redo them according to a global serialization order . Furthermore, Bayou permits clients to observe the results of all writes received by a server , including tentative writes whose conflicts have not been ultimately resolved. This paper presents the motivation for and design of these mechanisms and describes the experiences gained with an initial implementation of the system.

1,112 citations


Proceedings ArticleDOI
06 Mar 1995
TL;DR: An object-based information exchange model and a corresponding query language are defined that are well suited for integration of diverse information sources and used to integrate heterogeneous bibliographic information sources.
Abstract: We address the problem of providing integrated access to diverse and dynamic information sources. We explain how this problem differs from the traditional database integration problem and we focus on one aspect of the information integration problem, namely information exchange. We define an object-based information exchange model and a corresponding query language that we believe are well suited for integration of diverse information sources. We describe how, the model and language have been used to integrate heterogeneous bibliographic information sources. We also describe two general-purpose libraries we have implemented for object exchange between clients and servers. >

894 citations


Patent
25 Sep 1995
TL;DR: The Customer Contact Channel Changer as mentioned in this paper enables the integration of different customer contact channels such as live call center ACD (Automatic Call Distribution) agents, ADSI (Analog Display Services Interface) enhanced IVR (Interactive Voice Response) systems and WWW (World Wide Web) servers.
Abstract: This invention (The Customer Contact Channel Changer) enables the integration of different Customer Contact Channels such as live call center ACD (Automatic Call Distribution) agents, ADSI (Analog Display Services Interface) enhanced IVR (Interactive Voice Response) systems and WWW (World Wide Web) servers. The world wide web servers are used to allow customers with computer equipment to access information from an organizations databases in a self service mode. Frequently these customers have questions best answered by human ACD agents. With this invention the connection between the customer with the question and the agent with the answer is done quickly and efficiently with both parties sharing screens of common information. Also control is retained by the customer to make the call happen when they want it.

757 citations


Patent
07 Jun 1995
TL;DR: In this article, a hot redirection technique allows a user service session to be transferred from one application server to another (replicated) application server without termination of the service session, and various mechanisms are provided for efficiently reallocating application servers to different online services, and for allowing additional servers to be efficiently added to the network.
Abstract: An on-line services network includes application servers and Gateway microcomputers that are interconnected by a LAN. The Gateway microcomputers receive service requests which are transmitted over a WAN from client microcomputers operated by end users. Upon receiving a request to open a service, the Gateway microcomputers access a periodically-updated service map to locate the replicated application servers that are currently running the corresponding service application, and then apply a load balancing method (using server load data contained within the service map) to select an application server that has a relatively low processing load. A communications protocol between the client and Gateway microcomputers enables users to access multiple services simultaneously. A hot redirection technique allows a user service session to be transferred from one application server to another (replicated) application server without termination of the service session. Various mechanisms are provided for efficiently reallocating application servers to different on-line services, and for allowing additional servers to be efficiently added to the network.

735 citations


Patent
10 May 1995
TL;DR: The Scalable Multimedia Network (SMN) as discussed by the authors is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases.
Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein. The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

601 citations


Patent
18 Aug 1995
TL;DR: In this paper, access rights of users of a computer network with respect to data entities are specified by a relational database stored on one or more security servers, and an access rights cache on each application server caches the access rights lists of the users that are connected to the respective application server, so that user access rights to specific data entities can rapidly be determined.
Abstract: Access rights of users of a computer network with respect to data entities are specified by a relational database stored on one or more security servers. Application servers on the network that provide user access to the data entities generate queries to the relational database in order to obtain access rights lists of specific users. An access rights cache on each application server caches the access rights lists of the users that are connected to the respective application server, so that user access rights to specific data entities can rapidly be determined. Each user-specific access rights list includes a series of category identifiers plus a series of access rights values. The category identifiers specify categories of data entities to which the user has access, and the access rights values specify privilege levels of the users with respect to the corresponding data entity categories. The privilege levels are converted into specific access capabilities by application programs running on the application servers.

548 citations


Patent
16 Nov 1995
TL;DR: In this paper, the authors present a method for receiving alarms from multiple network management servers and applying a plurality of policy-based filters to the alarms, named and stored in a database, and application of the policybased filters may be scheduled for different times.
Abstract: Apparatus and method for receiving alarms from multiple network management servers and applying a plurality of policy-based filters to the alarms. The filters may be named and stored in a database, and application of the policy-based filters may be scheduled for different times. The same policy-based filters may be applied to one or more multiple network management applications. The invention allows greater control over which alarms get reported to network management applications and provides a means to ensure consistency of reported alarms across multiple network management applications.

520 citations


20 Nov 1995
TL;DR: This thesis explores how to support and also exploit the dynamic configurations and social settings characteristic of mobile systems and advances the following goals: enabling seamless interaction across devices; creating physical spaces that are responsive to users; and and building applications that are aware of the context of their use.
Abstract: Computer applications traditionally expect a static execution environment. However, this precondition is generally not possible for mobile systems, where the world around an application is constantly changing. This thesis explores how to support and also exploit the dynamic configurations and social settings characteristic of mobile systems. More specifically, it advances the following goals: (1) enabling seamless interaction across devices; (2) creating physical spaces that are responsive to users; and (3) and building applications that are aware of the context of their use. Examples of these goals are: continuing in your office a program started at home; using a PDA to control someone else's windowing UI; automatically canceling phone forwarding upon return to your office; having an airport overhead-display highlight the flight information viewers are likely to be interested in; easily locating and using the nearest printer or fax machine; and automatically turning off a PDA's audible e-mail notification when in a meeting. The contribution of this thesis is an architecture to support context-aware computing; that is, application adaptation triggered by such things as the location of use, the collection of nearby people, the presence of accessible devices and other kinds of objects, as well as changes to all these things over time. Three key issues are addressed: (1) the information needs of applications, (2) where applications get various pieces of information and (3) how information can be efficiently distributed. A dynamic environment communication model is introduced as a general mechanism for quickly and efficiently learning about changes occurring in the environment in a fault tolerant manner. For purposes of scalability, multiple dynamic environment servers store user, device, and, for each geographic region, context information. In order to efficiently disseminate information from these components to applications, a dynamic collection of multicast groups is employed. The thesis also describes a demonstration system based on the Xerox PARCTAB, a wireless palmtop computer.

519 citations


Proceedings Article
01 Jan 1995
TL;DR: In this paper, a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance is presented, and the authors determine that for the units which are often disconnected (sleepers) the best cache invalidization strategy is based on signatures previously used for efficient file comparison.
Abstract: In the mobile wireless computing environment of the future a large number of users equipped with low powered palm-top machines will query databases over the wireless communication channels. Palmtop based units will often be disconnected for prolonged periods of time due to the battery power saving measures; palmtops will also frequencly relocate between different cells and connect to different data servers at different times. Caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel. However, cache invalidation strategies will be severely affected by the disconnection and mobility of the clients. The server may no longer know which clients are currently residing under its cell and which of them are currently on. We propose a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance. We determine that for the units which are often disconnected (sleepers) the best cache invalidation strategy is based on signatures previously used for efficient file comparison. On the other hand, for units which are connected most of the time (workaholics), the best cache invalidation strategy is based on the periodic broadcast of changed data items.

509 citations


Journal ArticleDOI
TL;DR: This tutorial highlights the unique issues and data storage characteristics that concern designers in the real-time processing of multimedia data.
Abstract: Real-time processing of multimedia data is required of those who offer audio and video on-demand. This tutorial highlights the unique issues and data storage characteristics that concern designers. >

465 citations


Proceedings ArticleDOI
06 Mar 1995
TL;DR: The Garlic architecture is designed to be extensible to new kinds of data repositories, and access efficiency is addressed via a "middleware" query processor that uses database query optimization techniques to exploit the native associative search capabilities of the underlying data repositories.
Abstract: Provides an overview of the Garlic project, a new project at the IBM Almaden Research Center. The goal of this project is to develop a system and associated tools for the management of large quantities of heterogeneous multimedia information. Garlic permits traditional and multimedia data to he stored in a variety of existing data repositories, including databases, files, text managers, image managers, video servers, and so on; the data is seen through a unified schema expressed in an object-oriented data model and can be queried and manipulated using an object-oriented dialect of SQL, perhaps through an advanced query/browser tool that we are also developing. The Garlic architecture is designed to be extensible to new kinds of data repositories, and access efficiency is addressed via a "middleware" query processor that uses database query optimization techniques to exploit the native associative search capabilities of the underlying data repositories. >

Patent
21 Jul 1995
TL;DR: In this paper, a hierarchical communication system, arranged in a spanning tree configuration, is described in which wired and wireless communication networks exhibiting substantially different characteristics are employed in an overall scheme to link portable or mobile computing devices.
Abstract: A hierarchical communication system, arranged in a spanning tree configuration, is described in which wired and wireless communication networks exhibiting substantially different characteristics are employed in an overall scheme to link portable or mobile computing devices. Copies of data, program code and processing resources are migrated from their source toward requesting destinations based on request frequency, communication link costs and available local storage and/or processing resources. Each appropriately configured network device acts as an active participant in network migration. In addition, portable two-dimensional (2-D) code reading terminals are configured to wirelessly communicate compressed 2-D images toward stationary access servers that identify the code image through decoding and through comparison with a database of images that have previously been decoded and stored.

Patent
Peter Hussey1
21 Jun 1995
TL;DR: In this paper, a distributed system for processing queries for a server in a distributed processing environment is provided, which includes a plurality of clients disposed for communication with a database server through an electronic mail system.
Abstract: A networked system for processing queries for a server in a distributed processing environment is provided. The system includes a plurality of clients disposed for communication with a database server through an electronic mail system. The server includes an electronic mail interface for receiving queries submitted by the clients, and transmitting the corresponding response. A processor is also provided for processing the queries submitted from the clients, and submitting the queries on to the scheduler. The processor operates to provide bi-directional communication between the mail interface and the scheduler. In addition, the processor retrieves mail messages from the mail interface, translates them into a format recognized by the server, receives query results from the server, and returns the results with the appropriate user identification to the mail interface. A scheduler, provided in connection with the server, provides automated scheduled execution of the mail processor in accordance with a set of programmed tasks.

Journal ArticleDOI
TL;DR: In this paper, the authors describe a framework for itinerant agents that can be used to implement secure, remote applications in large, public networks such as the Internet or the IBM Global Network.
Abstract: Describes a framework for itinerant agents that can be used to implement secure, remote applications in large, public networks such as the Internet or the IBM Global Network. Itinerant agents are programs, dispatched from a source computer, that roam among a set of networked servers until they accomplish their task. This is an extension to the client/server model in which the client sends a portion of itself to the server for execution. An additional feature of itinerant agents is their ability to migrate from server to server, perhaps seeking one that can help with the user's task or perhaps collecting information from all of them. A major focus of the article is the agent meeting point, an abstraction that supports the interaction of agents with each other and server based resources The article begins with an overview of the operation of an itinerant agent framework and a review of previous work. The authors consider likely applications of itinerant agents and discuss one specific example in detail. They give an architectural description of the structure of itinerant agents, the languages employed to create them, and the execution environments required at the servers; and also a detailed description of how an itinerant agent is processed at a server. Security issues are then discussed and finally they consider the technical advantages of the itinerant agent framework and the services it enables. >

Journal ArticleDOI
TL;DR: The Method of Layers (MOL) is proposed to provide performance estimates for distributed applications that contain one or more layers of software servers and uses the mean value analysis (MVA) linearizer algorithm as a subprogram to assist in predicting model performance measures.
Abstract: Distributed applications are being developed that contain one or more layers of software servers. Software processes within such systems suffer contention delays both for shared hardware and at the software servers. The responsiveness of these systems is affected by the software design, the threading level and number of instances of software processes, and the allocation of processes to processors. The Method of Layers (MOL) is proposed to provide performance estimates for such systems. The MOL uses the mean value analysis (MVA) linearizer algorithm as a subprogram to assist in predicting model performance measures. >

Patent
07 Jun 1995
TL;DR: In this paper, a client-server session over the Internet involving hypertext files is described, where a client views a document transmitted by a content server with a standard program known as the browser.
Abstract: This invention relates to methods for providing access to network servers. In particular, the process described in the invention includes client-server sessions over the Internet involving hypertext files. In the hypertext environment, a client views a document transmitted by a content server with a standard program known as the browser. Each hypertext document or page contains links to other hypertext pages which the user may select to traverse. The user may also access a hypertext page by providing a conventional telephone number or other descriptor. The server maps such a telephone number or descriptor to a target page identifier using a translation database and automatically directs the client to retrieve the desired page.

Proceedings ArticleDOI
01 Oct 1995
TL;DR: The results of log-driven simulations of several variants of the proposed modifications to HTTP demonstrate the value of persistent connections.
Abstract: The success of the World-Wide Web is largely due to the simplicity, hence ease of implementation, of the Hypertext Transfer Protocol (HTTP). HTTP, however, makes inefficient use of network and server resources, and adds unnecessary latencies, by creating a new TCP connection for each request. Modifications to HTTP have been proposed that would transport multiple requests over each TCP connection. These modifications have led to debate over their actual impact on users, on servers, and on the network. This paper reports the results of log-driven simulations of several variants of the proposed modifications, which demonstrate the value of persistent connections.

Proceedings ArticleDOI
03 Dec 1995
TL;DR: The Rover toolkit combines relocatable dynamic objects and queued remote procedure calls to provide unique services for roving mobile applications and offers advantages for workstation applications by providing a uniform distributed object architecture.
Abstract: The Rover toolkit combines relocatable dynamic objects and queued remote procedure calls to provide unique services for roving mobile applications. A relocatable dynamic object is an object with a well-defined interface that can be dynamically loaded into a client computer from a server computer (or vice versa) to reduce client-server communication requirements. Queued remote procedure call is a communication system that permits applications to continue to make non-blocking remote procedure call requests even when a host is disconnected, with requests and responses being exchanged upon network reconnection. The challenges of mobile environments include intermittent connectivity, limited bandwidth, and channel-use optimization. Experimental results from a Rover-based mail reader, calendar program, and two non-blocking versions of World-Wide Web browsers show that Rover's services are a good match to these challenges. The Rover toolkit also offers advantages for workstation applications by providing a uniform distributed object architecture for code shipping, object caching, and asynchronous object invocation.

Journal ArticleDOI
TL;DR: Specific improvements developed for NTP Version 3 are described which have resulted in increased accuracy, stability and reliability in both local-area and wide-area networks and certain enhancements to the Unix operating system kernel software are described to realize submillisecond accuracies with fast workstations and networks.
Abstract: The Network Time Protocol (NTP) is widely deployed in the Internet to synchronize computer clocks to each other and to international standards via telephone modem, radio and satellite. The protocols and algorithms have evolved over more than a decade to produce the present NTP Version 3 specification and implementations. Most of the estimated deployment of 100000 NTP servers and clients enjoy synchronization to within a few tens of milliseconds in the Internet of today. This paper describes specific improvements developed for NTP Version 3 which have resulted in increased accuracy, stability and reliability in both local-area and wide-area networks. These include engineered refinements of several algorithms used to measure time differences between a local clock and a number of peer clocks in the network, as well as to select the best subset from among an ensemble of peer clocks and combine their differences to produce a local dock accuracy better than any in the ensemble. This paper also describes engineered refinements of the algorithms used to adjust the time and frequency of the local clock, which functions as a disciplined oscillator. The refinements provide automatic adjustment of algorithm parameters in response to prevailing network conditions, in order to minimize network traffic between clients and busy servers while maintaining the best accuracy. Finally, this paper describes certain enhancements to the Unix operating system kernel software in order to realize submillisecond accuracies with fast workstations and networks. >

Patent
06 Jun 1995
TL;DR: In this paper, the authors present a method and system for controlling access to entities on a network on which a plurality of servers are installed that use different operating systems, where a request is entered by a user at a workstation on the network to set access permissions to an entity in regard to a trustee, and various application programming interfaces are called to translate the generic request to set permissions on the entity into a format appropriate for the operating system that controls the entity.
Abstract: A method and system for controlling access to entities on a network on which a plurality of servers are installed that use different operating systems. A request is entered by a user at a workstation on the network to set access permissions to an entity on the network in regard to a trustee. In response to the request, various application programming interfaces (APIs) are called to translate the generic request to set permissions on the entity into a format appropriate for the operating system that controls the entity. Assuming that the user has the appropriate rights to set access permissions to the entity as requested, and assuming that the trustee identified by the user is among those who can have rights set to the entity, the request made by the user is granted. Entities include both "containers" and "objects." Entities are either software, such as directories (containers) and files (objects), or hardware, such as printers (objects).

Journal ArticleDOI
TL;DR: This article presents a brief overview of asymmetric environments and describes the approaches to broadcast disk organization, client cache management, and prefetching.
Abstract: Mobile computers and wireless networks are emerging technologies which promise to make ubiquitous computing a reality. One challenge that must be met in order to truly realize this potential is that of providing mobile clients with ubiquitous access to data. One way (and perhaps the only way) to address these challenges is to provide stationary server machines with a relatively high-bandwidth channel over which to broadcast data to a client population in anticipation of the need for that data by the clients. Such a system can be said to be asymmetric due to the disparity in the transmission capacities of clients and servers. We have proposed a mechanism called broadcast disks to provide database access in this environment as well as in other asymmetric systems such as cable and direct broadcast satellite television networks and information distribution services. The broadcast disk approach enables the creation of an arbitrarily fine-grained memory hierarchy on the broadcast medium. This hierarchy, combined with the inversion of the traditional relationship between clients and servers that occurs in a broadcast-based system, raises fundamental new issues for client cache management and data prefetching. In this article we present a brief overview of asymmetric environments and describe our approaches to broadcast disk organization, client cache management, and prefetching.

Proceedings ArticleDOI
01 Oct 1995
TL;DR: This paper considers the problem of choosing among a collection of replicated servers, focusing on the question of how to make choices that segregate client/server traffic according to network topology.
Abstract: In this paper we consider the problem of choosing among a collection of replicated servers, focusing on the question of how to make choices that segregate client/server traffic according to network topology. We explore the cost and effectiveness of a variety of approaches, ranging from those requiring routing layer support (e.g., anycast) to those that build location databases using application-level probe tools like traceroute. We uncover a number of tradeoffs between effectiveness, network cost, ease of deployment, and portability across different types of networks. We performed our experiments using a simulation parameterized by a topology collected from 7 survey sites across the United States, exploring a global collection of Network Time Protocol servers.

Patent
23 Jun 1995
TL;DR: In this article, the authors propose a distributed synchronization system for replicated files in distributed systems using a library which replaces a standard I/O library, and may thus be employed without modification to hardware or the operating system.
Abstract: Techniques for providing replicated files in a distributed system. A replicated file has a set of copies in components of the distributed system. Operations on the copies have the same semantics for the application processes accessing them as operations on a single copy of a file in a system where all processes execute on the same host. These semantics are achieved by means of a distributed synchronization system. Each replicated file has a read token and a write token. In order for an application process to perform an operation on a replicated file, the token required for the operation must be in the process's host and the process must have access to the token. Tokens are passed between hosts by token servers which respond to requests for tokens from application processes and from other token servers. The techniques are implemented using a library which replaces a standard I/O library, and may thus be employed without modification to hardware or the operating system.

Patent
07 Jun 1995
TL;DR: Distributed Integration Solution (DIS) as discussed by the authors is a set of capsule objects which perform programmable functions upon a received command from a web server control program agent for retrieving, from a database gateway coupled to a plurality of database resources upon a single request made from a Hypertext document, requested information from multiple data bases located at different types of databases geograhically dispersed, performing calculations, formatting, and other services prior to reporting to the web browser or to other locations, in a selected format, as in a display, fax, printer, and to customer installations or to TV
Abstract: A World Wide Web browser makes requests to web servers on a network which receive and fulfill requests as an agent of the browser client, organizing distributed sub-agents as distributed integration solution (DIS) servers on an intranet network supporting the web server which also has an access agent servers accessible over the Internet. DIS servers execute selected capsule objects which perform programmable functions upon a received command from a web server control program agent for retrieving, from a database gateway coupled to a plurality of database resources upon a single request made from a Hypertext document, requested information from multiple data bases located at different types of databases geograhically dispersed, performing calculations, formatting, and other services prior to reporting to the web browser or to other locations, in a selected format, as in a display, fax, printer, and to customer installations or to TV video subscribers, with account tracking.

Patent
08 Sep 1995
TL;DR: In this article, a system and method for providing annotation overlays from diverse sources of commentary for World Wide Web documents is disclosed, where annotation overlayers from a particular source are stored on one or more overlay servers, which are connected to the Web.
Abstract: A system and method for providing annotation overlays from diverse sources of commentary for World-Wide Web documents is disclosed. Sources of commentary contribute annotation overlays regarding particular documents on the World-Wide Web. The annotation overlays from a particular source are stored on one or more overlay servers, which are connected to the Web. A user of a Web browser opens an annotation proxy server between the Web browser and the Web servers that intercepts all documents retrieved by the Web browser and merges with the retrieved documents commentary from sources designated by the user of the Web browser that refer to the requested documents. Multiple annotation overlay proxies can be serially connected. The annotation proxy can perform the merge operation by first creating a local annotation directory of annotation overlays from sources designated by the user then, when the user requests a document, merging with the requested document information only from the annotation directory. Alternatively, the annotation proxy can perform the merge operation on the fly by pulling the annotation overlays directly from the Web servers without the use of a local annotation directory.

Patent
14 Mar 1995
TL;DR: In this paper, the authors propose an Integrity Server computer for economically protecting the data of a computer network's servers, and providing hot standby access to up-to-date copies of a failed server.
Abstract: An Integrity Server computer for economically protecting the data of a computer network's servers, and providing hot standby access to up-to-date copies of the data of a failed server. As the servers' files are created or modified, they are copied to the Integrity Server. When one of the servers fails, the Integrity Server fills in for the failed server, transparently providing the file service of the failed server to network clients. The invention provides novel methods for managing the data stored on the Integrity Server, so that the standby files are stored on low-cost media such as tape, but are quickly copied to disk when a protected server fails. The invention also provides methods for re-establishing connections between clients and servers, and communicating packets between network nodes, to allow the Integrity Server to stand-in for a failed server without requiring reconfiguration of the network clients.

Patent
29 Nov 1995
TL;DR: In this paper, a message driven processor (450) operates as middleware between clients (400) and back-end hosts or servers (440) in a large client-server system to reduce the number of concurrent sessions required to be supported by the network and to allow a common client user interface to divergent backend systems.
Abstract: A message driven processor (450) operates as middleware between clients (400) and back-end hosts or servers (440) in a large client-server system to reduce the number of concurrent sessions required to be supported by the network and to allow a common client user interface to divergent back-end systems. High level requests from a client (400) in support of a business function are translated into workflows which may involve multiple requests to back-end servers by the message driven processor (450). Information resulting from workflows and information retrieved from back-end servers may be integrated into a single reply message to the requesting client (400).

Patent
30 Jan 1995
TL;DR: An apparatus and method for allocating a data file across a plurality of media servers in a network, wherein each media server has associated with one or more levels of I/O devices organized in a hierarchical manner is provided in this article.
Abstract: An apparatus and method is provided for allocating a data file across a plurality of media servers in a network, wherein each media server has associated therewith one or more levels of I/O devices organized in a hierarchical manner An attempt is made to allocate the storage of data across the I/O devices in such a way that the bandwidth imposed on the devices when the data file is sequentially accessed will be balanced, and optimum use of I/O bandwidths at all points in the system is achieved This balancing can be done by incorporating knowledge regarding various bottlenecks in the system into the decisionmaking process required for distributing the data blocks The method and apparatus further allows bandwidths to be allocated to various clients in the system at the time a data file is opened Various checks are provided at the time a data file is accessed to ensure that the data rates actually imposed by the requesting client do not exceed that requested by the client at the time the data file was opened The invention allows for much more efficient use of the I/O resources in a system and ensures that a given configuration will be able to support client requests

Journal ArticleDOI
TL;DR: In this article, the authors consider the problem of assigning each customer to an appropriate server in a manner that will balance the load on the servers and derive tight bounds on the competitive ratio in both deterministic and randomized cases, and conclude that randomized algorithms differ from deterministic ones by precisely a constant factor.

Patent
19 May 1995
Abstract: A primary server/standby server network configuration according to the invention includes a primary server executing network operating system software and a standby server monitoring for the proper operation of the primary server, where both the primary server and the standby server are connected to a storage system. If the primary server fails, the standby server instructs the storage system to switch its hardware connections to the standby server, allowing the standby server to boot the operating system. This instruction is done via in-band signaling. Further, multiple primary servers can be backed up by a single standby server.