This paper describes a network storage system, called Venti, intended for archival data. In this system, a unique hash of a block's contents acts as the block identifier for read and write operations. This approach enforces a write-once policy, preventing accidental or malicious destruction of data. In addition, duplicate copies of a block can be coalesced, reducing the consumption of storage and simplifying the implementation of clients. Venti is a building block for constructing a variety of storage applications such as logical backup, physical backup, and snapshot file systems.

In this report, we describe the collection of file system traces from three different environments. By using the auditing system to collect traces on client machines, we are able to get detailed traces with minimal kernel changes. We then present results of traffic analysis on the traces, contrasting them with those from previous studies. Based on these results, we argue that file systems must optimize disk layout for good read performance. 1

Self-securing storage prevents intruders from undetectably tampering with or permanently deleting stored data. To accomplish this, self-securing storage devices internally audit all requests and keep old versions of data for a window of time, regardless of the commands received from potentially compromised host operating systems. Within the window, system administrators have this valuable information for intrusion diagnosis and recovery. Our implementation, called S4, combines log-structuring with journal-based metadata to minimize the performance costs of comprehensive versioning. Experiments show that self-securing storage devices can deliver performance that is comparable with conventional storage systems. In addition, analyses indicate that several weeks worth of all versions can reasonably be kept on state-of-the-art disks, especially when differencing and compression technologies are employed.

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IRON FILE SYSTEMSVijayan Prabhakaran Disk drives are widely used as a primary medium for storing information.While commodity file systems trust disks to either work or fail completely, modern disks exhibit complex failure modes such as latent sector faults and block corrup-tions, where only portions of a disk fail.

In this paper we describe the architecture and design of a new file system, XFS, for Silicon Graphics’ IRIX operating system. It is a general purpose file system for use on both workstations and servers. The focus of the paper is on the mechanisms used by XFS to scale capacity and performance in supporting very large file systems. The large file system support includes mechanisms for managing large files, large numbers of files, large directories, and very high performance I/O. In discussing the mechanisms used for scalability we include both descriptions of the XFS on-disk data structures and analyses of why they were chosen. We discuss in detail our use of B+ trees in place of many of the more traditional linear file system structures. XFS has been shipping to customers since December of 1994 in a version of IRIX 5.3, and we are continuing to improve its performance and add features in upcoming releases. We include performance results from running on the latest version of XFS to demonstrate the viability of our design.

Track-aligned extents (traxtents) utilize disk-specific knowledge to match access patterns to the strengths of modern disks. By allocating and accessing related data on disk track boundaries, a system can avoid most rotational latency and track crossing overheads. Avoiding these overheads can increase disk access efficiency by up to 50 % for mid-sized requests (100-500 KB). This paper describes traxtents, algorithms for detecting track boundaries, and some uses of traxtents in file systems and video servers. For large-file workloads, a version of FreeBSD's FFS implementation that exploits traxtents reduces application run times by up to 20 % compared to the original version. A video server using traxtent-based requests can support 56 % more concurrent streams at the same startup latency and buffer space. For LFS, 44 % lower overall write cost for track-sized segments can be achieved.

This paper describes a new version of the Network File System (NFS) that supports access to files larger than 4GB and increases sequential write throughput sevenfold when compared to unaccelerated NFS Version 2. NFS Version 3 maintains the stateless server design and simple crash recovery of NFS Version 2, and the philosophy of building a distributed file service from cooperating protocols. We describe the protocol and its implementation, and provide initial performance measurements. We then describe the implementation effort. Finally, we contrast this work with other distributed file systems and discuss future revisions of NFS. 1.

Research results show that while Log-Structured File Systems (LFS) offer the potential for dramatically improved file system performance, the cleaner can seriously degrade performance, by as much as 40 % in transaction processing workloads [9]. Our goal is to examine trace data from live file systems and use those to derive simple heuristics that will permit the cleaner to run without interfering with normal file access. Our results show that trivial heuristics perform very well, allowing 97 % of all cleaning on the most heavily loaded system we studied to be done in the background. 1.

In this paper, we study how to minimize the latency of small synchronous writes to disks. The basic approach is to write to free sectors that are near the current disk head location by leveraging the embedded processor core inside the disk. We develop a number of analytical models to demonstrate the performance potential of this approach. We then present the design of a virtual log, a log whose entries are not physically contiguous, and a variation of the log-structured file system based on this approach. The virtual log based file systems can e#ciently support small synchronous writes without extra hardware support while retaining the advantages of LFS including its potential to support transactional semantics. We compare our approach against traditional update-in-place and logging systems by modifying the Solaris kernel to serve as a simulation engine. Our evaluations show that random synchronous updates on an unmodified UFS execute up to an order of magnitude faster on a virtual log...