Distributed file systems have become popular because they allow information to be shared be between computers in a natural way. A distributed file system often forms a central building block in a distributed system. Currently most distributed file systems are built using a communications interface that transfers messages about files between machines. This thesis proposes a different, lower level, communications interface. This `block-based' interface exchanges information about the blocks that make up the file but not about the files themselves. No other distributed file system is built this way. By demonstrating that a distributed file system can be implemented in a block-based manner, this thesis opens the way for many advances in distributed file systems. These include a reduction of the processing required at the server, uniformity in managing file blocks and fine-grained placement and replication of data. The simple communications model also lends itself to efficient implementation both at the server and in the communications protocols that support the interface. These advantages come at the cost of a more complex client implementation and the need for a lower level consistency mechanism. A block-based distributed file system (BB-NFS) has been implemented. BB-NFS provides the Unix file system interface and demonstrates the feasibility and implementability of the block-based approach. Experience with the implementation lead to the development of a lock cache mechanism which gives a large improvement in the performance of the prototype. Although it has not been directly measured it is plausible that the prototype will perform better than the file based approach. The block-based approach has much to offer future distributed file system developers. This thesis introduces the approach and its advantages, demonstrates its feasibility and shows that it can be implemented in a way that performs well.

I ljuset av en upphovsrätt som har till syfte att skapa incitament för nyskapande, innovation och tillgå allmänheten med kultur krävs förändring av lagstiftningen på området. Detta för att säkerställa de ensamrättigheter, rätt till exemplarframställning samt rätt till tillgängliggörande för allmänheten, en upphovsman erhåller till dennes verk. Idag ger förvisso den gällande rätten dessa rättigheter skydd. Emellertid bryter många svenskar mot detta skydd och gör intrång i den till upphovsmannen eller rättighetsinnehavaren knutna upphovsrätten. Att en förändring är påkallat inom området står klart eftersom ytterst få av dem som gör intrång i upphovsrätten åläggs ansvar för gärningen.  Dock finns olika synpunkter på i vilken riktning förändringen ska ske. En stor opposition till upphovsrättens gällande lagstiftning som menar att stora delar av den bör ändras för att legalisera fildelning. Samtidigt försöker förespråkarna för upphovsrätten hindra utvecklingen som innebär att intrång i upphovsrätten sker genom ny restriktivare lagstiftning.  Uppsatsen behandlar de skäl och argument som de båda sidorna framställer. Vidare tar uppsatsen upp de olika förändringar och lösningar som skälen och argumenten har utmynnat i.

OurFileSystem (OFS) is a peer-to-peer file and metadata sharing program. Peers freely join the network, but must be granted access to groups in which metadata and files are shared. Any peer may create a group and grant others access to the group. Group members have different degrees of authority to grant others access and set their authority. Metadata for files is created by users within the context of a group and distributed to all members of the group in the form of a post. Post templates can be created to set fields of metadata. Templates are distributed to all members of a group, and one can be selected when creating a post or searching for files. Metadata in posts is indexed, and sophisticated search on the metadata can be performed locally to help users find files of interest quickly. Files found during a search may be downloaded from peers upon request. Pieces of files are downloaded from as many different peers as possible to maximize bandwidth. Peers within a group may also be marked as bad locally. If a user marks another peer as bad within the context of a group, posts from that peer to the group are deleted and not shared with others. Furthermore, any peer that was granted access by a peer marked as bad is also marked bad. No further posts or authorizations are ever accepted from any peer marked as bad. OFS also supports small public and private messages, which are distributed to all peers in the network. Private messages are encrypted so only the intended peer can decrypt the message. Lastly OFS integrates well with anonymous overlay networks that support SOCKS proxies, such as TOR. I2P support has also been explicitly added. / text

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This thesis details the integration of a common collaboration technique, desktop sharing, into a virtual world environment. Previous literature shows no intersection between these fields. This thesis will illustrate that existing collaboration technology can be integrated into virtual worlds with a minimal amount of effort. Outlined in this thesis are the developmental and procedural challenges encountered in demonstrating seamless desktop sharing in a virtual environment and a stress test of the integrated system revealing that the inclusion of desktop sharing resulted in minor performance loss. The Problem Current virtual world technology has limited capability for collaboration because of a lack of collaboration tools. This thesis proposes that it is feasible to take a common collaboration tool such as desktop sharing and introduce it into a virtual world. / Department of Computer Science

Tuning a computer system effectively requires prior studies on the performance of the system. There are different types of tools available to measure a system: hardware, firmware and software. This thesis presents the design and implementation of an event monitor, which is one type of software tools. The event monitor was developed on a SUN1 workstation running UNIX 4.2bsd version 1.4. Six types of events were selected to be measured, namely transactions, logins/logouts, pageins, pageouts, disk I/Os and forks/exits. The operating system was modified to include probes to trap these events. For a final testing of the event monitor, it was ported and installed onto a SUN3 workstation running UNIX 4.2bsd version 3.2. Measurements collected were analyzed by a capacity planning package condenser. The results give an indication of the system workload and the system performance. Benchmarks were also set up to measure the overhead incurred by the event monitor. / Science, Faculty of / Computer Science, Department of / Graduate

A performance experiment on a PDP 11/45 running under UNIX is described. The purpose is to discover the major influences in the system and their relationships in an attempt to analyze the performance of the system and predict the effect on performance of possible hardware and workload changes. A suitable performance parameter is developed and the workload, hardware and internal system parameters are determined. Tools are constructed to record these parameters. A controlled experiment, using a synthetic workload is then conducted. The results are analyzed using regression analysis and suitable equations are obtained. Sample applications are given. The merits of the relationships, as well as the suitability of the tools developed and methods used, are discussed. / Science, Faculty of / Computer Science, Department of / Graduate

Supercomputing application simulations on hundreds of thousands of cores produce vast amounts of data that need to be analyzed on smaller-scale clusters to glean insights. The process is referred to as an end-to-end workflow. Extant workflow systems are stymied by the storage wall, resulting from both the disk-based parallel file system (PFS) failing to keep pace with the compute and memory subsystems as well as the inefficiencies in end-to-end workflow processing. In the post-petaflop era, supercomputers are provisioned with flash devices, as an intermediary between compute nodes and the PFS, enabling novel paradigms not just for expediting I/O, but also for the in-situ analysis of the simulation output data on the flash device. An array of such active flash elements allows us to fundamentally rethink the way data analysis workflows interact with storage systems. By blending the flash storage array and data analysis together in a seamless fashion, we create an analysis workflow-aware storage system, AnalyzeThis. Our guiding principle is that analysis-awareness be deeply ingrained in each and every layer of the storage system—active flash fabric, analysis object abstraction layer, scheduling layer within the storage, and an easy-to-use file system interface—thereby elevating data analyses as first-class citizens. Together, these concepts transform AnalyzeThis into a potent analytics-aware appliance. / Master of Science

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / Although the wireless data transmission technologies have evolved significantly, data recording devices are still being used because of the limitations of data rates and reliability issues over wireless environment in the avionics, military, space etc. Payload has limitation of weight. In addition, storage has limitation of capacity. So, we need to research about a data recording structure within a limited amount of memory. In this paper, we propose a new data recording structure through a condition necessary for efficient use of memory. The proposed structure has an equivalent function as other recording systems. But, it uses less memory than the other equivalent recording structures.

Well replicated tree-ring samples were collected, dated and measured for California west of the Sierra Nevada, eastern Oregon and the northern Great Basin. A computer program was developed and used to check crossdating quality. Another computer program to generate and analyze tree-ring chronologies was evaluated, further developed cooperatively and used to produce chronologies for the dated site collections. This report contains these site chronologies in three versions along with site descriptions and chronology statistics. Users manuals are included for the two computer programs. The effect on a chronology of poor crossdating is discussed, and a study of standardization of tree-ring measurement series is reported. Some new techniques are described for processing tree-ring samples.