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The axes ordering in PCP presents a particular story from the data based on the user perception of PCP polylines. Existing works focus on directly optimizing for PCP axes ordering based on some common analysis tasks like clustering, neighborhood, and correlation. However, direct optimization for PCP axes based on these common properties is restrictive because it does not account for multiple properties occurring between the axes, and for local properties that occur in small regions in the data. Also, many of these techniques do not support the human-in-the-loop (HIL) paradigm, which is crucial (i) for explainability and (ii) in cases where no single reordering scheme fits the user goals. To alleviate these problems, we present PC-Expo, a real-time visual analytics framework for all-in-one PCP line pattern detection, and axes reordering. We studied the connection of line patterns in PCPs with different data analysis tasks and datasets. PC-Expo expands prior work on PCP axes reordering by developing real-time, local detection schemes for the 12 most common analysis tasks (properties). Users can choose the story they want to present with PCPs by optimizing directly over their choice of properties. These properties can be ranked, or combined using individual weights, creating a custom optimization scheme for axes reordering. Users can control the granularity at which they want to work with their detection scheme in the data, allowing exploration of local regions. PC-Expo also supports HIL axes reordering via local-property visualization, which shows the regions of granular activity for every axis pair. Local-property visualization is helpful for PCP axes reordering based on multiple properties, when no single reordering scheme fits the user goals., Comment: Pre-print of the accepted paper at Transactions of Visualization and Computer Graphics Forum (TVCG), 2022

Deduplication has become essential in disk-based backup systems, but there have been few long-term studies of backup workloads. Most past studies either were of a small static snapshot or covered only a short period that was not representative of how a backup system evolves over time. For this paper, we collected 21 months of data from a shared user file system; 33 users and over 4,000 snapshots are covered. We analyzed the data set for a variety of essential characteristics. However, our primary focus was individual user data. Despite apparently similar roles and behavior in all of our users, we found significant differences in their deduplication ratios. Moreover, the data that some users share with others had a much higher deduplication ratio than average. We analyze this behavior and make recommendations for future deduplication systems design.

Modern file systems assume the use of disk, a system-wide performance bottleneck for over a decade. Current disk caching and RAM file systems either impose high overhead to access memory content or fail to provide mechanisms to achieve data persistence across reboots.The Conquest file system is based on the observation that memory is becoming inexpensive, which enables all file system services to be delivered from memory, except for providing large storage capacity. Unlike caching, Conquest uses memory with battery backup as persistent storage, and provides specialized and separate data paths to memory and disk. Therefore, the memory data path contains no disk-related complexity. The disk data path consists of optimizations only for the specialized disk usage pattern.Compared to a memory-based file system, Conquest incurs little performance overhead. Compared to several disk-based file systems, Conquest achieves 1.3x to 19x faster memory performance, and 1.4x to 2.0x faster performance when exercising both memory and disk. Conquest realizes most of the benefits of persistent RAM at a fraction of the cost of a RAM-only solution. It also demonstrates that disk-related optimizations impose high overheads for accessing memory content in a memory-rich environment.

Constructing multipath routes in MANETs is important for providing reliable delivery, load balancing, and bandwidth aggregation. However, popular multipath routing approaches fail to produce spatially disjoint routes in a simple and cost-effective manner, and existing single-path approaches cannot be easily modified to produce multiple disjoint routes. In this paper we propose Electric-Field-Based Routing (EFR) as a reliable framework for routing in MANETs by applying the concept of electric field lines. Our location-based protocol naturally provides spatially disjoint routes based on the shapes of these lines. The computation is highly localized and requires no explicit coordination among routes. EFR can also be easily extended to offer load-balancing, bandwidth aggregation, and power management. Through simulation, EFR shows a higher delivery ratio and lower overhead under high mobility, high network loads, and network failures compared to popular multipath and location-based schemes. EFR also demonstrates high resiliency to DoS attacks.

This research proposes and tests an approach to engineering distributed file systems that are aimed at wide-scale, Internet-based use. The premise is that replication is essential to deliver performance and availability, yet the traditional conservative replica consistency algorithms do not scale to this environment. Our Ficus replicated file system uses a single-copy availability, optimistic update policy with reconciliation algorithms that reliably detect concurrent updates and automatically restore the consistency of directory replicas. The system uses the peer-to-peer model in which all machines are architectural equals but still permits configuration in a client-server arrangement where appropriate. Ficus has been used for six years at several geographically scattered installations. This paper details and evaluates the use of optimistic replica consistency, automatic update conflict detection and repair, the peer-to-peer (as opposed to client-server) interaction model, and the stackable file system architecture in the design and construction of Ficus. The paper concludes with a number of lessons learned from the experience of designing, building, measuring, and living with an optimistically replicated file system. © 1998 John Wiley & Sons, Ltd.

In this panel, we will address questions regarding the development and execution of one type of industry-academic collaboration - corporate-sponsored projects. As representatives of programs at both public and private institutions, we will address a set of questions related to these programs. We have prepared an initial list that will be augmented with questions submitted and voted on by conference participants in advance of the session. After we have presented our prepared responses, the balance of the session will be dedicated to open discussion with audience members.

Summary form only given. The Conquest file system is designed to provide a transition from disk- to persistent-RAM-based storage. Initially, we assume 2 to 4 Gbytes of persistent RAM and the popular single-user desktop environment. Unlike other memory file systems, Conquest can incrementally assume more responsibility for in-core storage as memory prices decline. The Conquest approach realizes most of the benefits of persistent-RAM-based file systems before persistent RAM becomes cheaply abundant. Conquest also benefits from the removal of disks as the primary storage by identifying disk-related complexities and isolating them from the critical path where possible. The Conquest prototype is operational under Linux 2.4.2. It is POSIX compliant and supports both in-core and on-disk storage.

Future network intruders will probably use an organized army of malicious nodes (here called "malnodes", or collectively a "malnet") to deliver many different attacks, rather than recruiting a disorganized set of compromised nodes per attack. However, partly due to the lack of understanding of the resiliency and efficiency a malnet can have, countering malnets has been ineffective. This paper begins to address this deficiency. Through calculation and simulation for three representative malnets - random, small-world, and Gnutella-like - we show that extremely resilient malnets can be formed to deliver attack code quickly. In particular, we show that disconnecting malnets is possible, but extremely naive approaches such as randomly disinfecting malnodes will not suffice, and effective defenses must either happen very quickly during a second-wave attack, or take effect prior to it.

Optimistic replication of data is a widely used tool for mobile environments, but the behavior of concurrent conflicting updates caused by the relaxed consistency model is poorly understood. Through analytical modeling, we derive an exact bound for conflict rates for the common case of two replicas. The shape of the two-replica analytic curve matches well with simulation results at 50 replicas. Our result shows that (1) both frequently and infrequently synchronized mobile machines operate in the low regions of the conflict-rate curve; (2) conflict rate is not well suited for comparing systems, since multiple system settings can result in the same conflict rate number; and (3) the conflict rate is highly dependent on the characteristics of data flow paths.

One approach to detecting insider misbehavior is to monitor system call activity and watch for danger signs or unusual behavior. We describe an experimental system designed to test this approach. We tested the system's ability to detect common insider misbehavior by examining file system and process-related system calls. Our results show that this approach can detect many such activities.

Reducing power consumption for server-class computers is important, since increased energy usage causes more heat dissipation, greater cooling requirements, reduced computational density, and higher operating costs. For a typical data center, storage accounts for 27% of energy consumption. Conventional server-class RAIDs cannot easily reduce power because loads are balanced to use all disks, even for light loads. We have built the power-aware RAID (PARAID), which reduces energy use of commodity server-class disks without specialized hardware. PARAID uses a skewed striping pattern to adapt to the system load by varying the number of powered disks. By spinning disks down during light loads, PARAID can reduce power consumption, while still meeting performance demands, by matching the number of powered disks to the system load. Reliability is achieved by limiting disk power cycles and using different RAID encoding schemes. Based on our five-disk prototype, PARAID uses up to 34% less power than conventional RAIDs while achieving similar performance and reliability.