Browsing by Author "Post, Ansley"

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    Autonomous storage management for low-end computing environments
    (2011) Post, Ansley; Druschel, Peter
    To make storage management transparent to users, enterprises rely on expensive storage infrastructure, such as high end storage appliances, tape robots, and offsite storage facilities, maintained by full-time professional system administrators. From the user's perspective access to data is seamless regardless of location, backup requires no periodic, manual action by the user, and help is available to recover from storage problems. The equipment and administrators protect users from the loss of data due to failures, such as device crashes, user errors, or virii, as well as being inconvenienced by the unavailability of critical files. Home users and small businesses must manage increasing amounts of important data distributed among an increasing number of storage devices. At the same time, expert system administration and specialized backup hardware are rarely available in these environments, due to their high cost. Users must make do with error-prone, manual, and time-consuming ad hoc solutions, such as periodically copying data to an external hard drive. Non-technical users are likely to make mistakes, which could result in the loss of a critical piece of data, such as a tax return, customer database, or an irreplaceable digital photograph. In this thesis, we show how to provide transparent storage management for home and small business users We introduce two new systems: The first, PodBase, transparently ensures availability and durability for mobile, personal devices that are mostly disconnected. The second, SLStore, provides enterprise-level data safety (e.g. protection from user error, software faults, or virus infection) without requiring expert administration or expensive hardware. Experimental results show that both systems are feasible, perform well, require minimal user attention, and do not depend on expert administration during disaster-free operation. PodBase relieves home users of many of the burdens of managing data on their personal devices. In the home environment, users typically have a large number of personal devices, many of them mobile devices, each of which contain storage, and which connect to each other intermittently. Each of these devices contain data that must be made durable, and available on other storage devices. Ensuring durability and availability is difficult and tiresome for non-expert users, as they must keep track of what data is stored on which devices. PodBase transparently ensures the durability of data despite the loss or failure of a subset of devices; at the same time, PodBase aims to make data available on all the devices appropriate for a given data type. PodBase takes advantage of storage resources and network bandwidth between devices that typically goes unused. The system uses an adaptive replication algorithm, which makes replication transparent to the user, even when complex replication strategies are necessary. Results from a prototype deployment in a small community of users show that PodBase can ensure the durability and availability of data stored on personal devices under a wide range of conditions with minimal user attention. Our second system, SLStore, brings enterprise-level data protection to home office and small business computing. It ensures that data can be recovered despite incidents like accidental data deletion, data corruption resulting from software errors or security breaches, or even catastrophic storage failure. However, unlike enterprise solutions, SLStore does riot require professional system administrators, expensive backup hard- ware, or routine, manual actions on the part of the user. The system relies on storage leases, which ensure that data cannot be overwritten for a pre-determined period, and an adaptive storage management layer which automatically adapts the level of backup to the storage available. We show that this system is both practical, reliable and easy to manage, even in the presence of hardware and software faults.
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    Self-Organizing Hierarchical Routing for Scalable Ad Hoc Networking
    (2005-02-08) Druschel, Peter; Du, Shu; Johnson, David B.; Khan, Muhammed; PalChaudhuri, Santashil; Post, Ansley; Riedi, Rudolf H.; Saha, Amit
    As wireless devices become more pervasive, mobile ad hoc networks are becoming increasingly important, motivating the development of highly scalable ad hoc networking techniques. In this paper, we present the design and evaluation of a novel protocol for scalable routing in ad hoc networks, as part of the Safari project. Safari leverages and integrates research in both ad hoc networking and peer-to-peer networking. We develop a probabilistic, elf-organizing network hierarchy formation protocol that recursively forms the nodes of the ad hoc network into an adaptive, proximity-based hierarchy of cells. We develop a hybrid routing protocol that uses this hierarchy, with reactive and proactive routing, to scale to large number of nodes. The mapping of unique node identifiers to hierarchical addresses is done using a distributed hash table that leverages the hierarchical network structure. We evaluate this design through analysis and simulations, under increasing network size, increasing fraction of mobile nodes, and increasing offered traffic load. Our analysis is well matched by our simulations, and our results demonstrate the protocol's scalability.