Modern distributed applications often have to make a choice about how to main- tain data within the system. Distributed storage systems are often self- contained in a single cluster or are a black box as data placement is unknown by an applica- tion. Using wide area distributed storage either means using multiple APIs or loss of control of data placement. This work introduces Sage, a distributed filesystem that aggregates multiple backends under a common API. It also gives applications the ability to decide where file data is stored in the aggregation. By leveraging Sage, users can create applications using multiple distributed backends with the same API, and still decide where to physically store any given file. Sage uses a layered design where API calls are translated into the appropriate set of backend calls then sent to the correct physical backend. This way Sage can hold many backends at once mak- ing them appear as the same filesystem. The performance overhead of using Sage is shown to be minimal over directly using the backend stores, and Sage is also shown to scale with respect to backends used. A case study shows file placement in action and how applications can take advantage of the feature. / Graduate

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Virtual machines (VMs) are useful mechanisms for better resource utilization, support for special software configurations, and the movement of packaged software across systems. Exploiting VM advantages in a production setting, however, often requires computer systems with the smallest possible disk-size footprint. Administrators and programmers who create VMs, however, may need a robust set of tools for development. This introduces an important conflict: Minimalism demands that packaged software be as small as possible, while completeness demands that nothing required is missing. We present a system called Lilliputia, which combines resource usage monitoring (through a Linux FUSE filesystem we created called StatFS), with a filtered cloning system, which copies an existing physical or virtual machine into a smaller clone. Finally, we show how Lilliputia can reduce the size of the Trellis Network-Attached-Storage (NAS) Bridge Appliance and the Chemical Shift to 3D Structure protein structure predictor to 10-30% of their original size.

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A runtime file system checker protects file-system metadata integrity. It checks the consistency of file system update operations before they are committed to disk, thus preventing corrupted updates from reaching the disk. In this thesis, we describe our experiences with building Brunch, a runtime checker for an emerging Linux file system called Btrfs. Btrfs supports many modern file-system features that pose challenges in designing a robust checker. We find that the runtime consistency checks need to be expressed clearly so that they can be reasoned about and implemented reliably, and thus we propose writing the checks declaratively. This approach reduces the complexity of the checks, ensures their independence, and helps identify the correct abstractions in the checker. It also shows how the checker can be designed to handle arbitrary file system corruption. Our results show that runtime consistency checking is still viable for complex, modern file systems.

A runtime file system checker protects file-system metadata integrity. It checks the consistency of file system update operations before they are committed to disk, thus preventing corrupted updates from reaching the disk. In this thesis, we describe our experiences with building Brunch, a runtime checker for an emerging Linux file system called Btrfs. Btrfs supports many modern file-system features that pose challenges in designing a robust checker. We find that the runtime consistency checks need to be expressed clearly so that they can be reasoned about and implemented reliably, and thus we propose writing the checks declaratively. This approach reduces the complexity of the checks, ensures their independence, and helps identify the correct abstractions in the checker. It also shows how the checker can be designed to handle arbitrary file system corruption. Our results show that runtime consistency checking is still viable for complex, modern file systems.

This thesis is about encrypted filesystems and is aimed mainly for Linux solutions. At first there is explained why is it necessary to encrypt your data at all. Next is written about pros and cons of encrypting methods such as whole disk encryption, partition encryption, container encryption and file encryption. After the introduction there are mentioned most common security issues which can help attacker to decrypt your data or modify them. Furthermore this thesis contains short description about the most often used encrypted filesystems. There is also small how-to for the most important encrypted filesystems available in Linux and comparison of their speed. Next part of this thesis contains dm-crypt and LUKS description. In the last chapter all information are concluded. There is also mentioned benefit of this work and possibilities, what can be done in future.

The goal of this master thesis is to analyze Open Source resources for loadbalancing and high availability, with aim on areas of its typical usage. These areas are particularly solutions of network infrastructure (routers, loadbalancers), generally network and internet services and parallel filesystems. Next part of this thesis is analysis of design, implementation and plans of subsequent advancement of an fast growing Internet project. The effect of this growth is necessity of solving scalability on all levels. The last part is performance analysis of individual loadbalancing methods in the Linux Virtual Server project.