The design and implementation of an extensible network backup system in realtime

Objectives: To determine if an on‐line information system is superior to a conventional ambulance file system regarding the possibility of retrieving information as follow‐up in daily use and also with reference to disaster situations. Materials and methods: The study was designed as a prospective study where two systems that have been operational for several years were compared. One system was a system primarily built for on‐line registration and the other a conventional ambulance file system. Results: In all aspects data regarding ambulance missions and patients were more thoroughly registered in the conventional file system. Also data were easier to retrieve with less time consumption compared to the on‐line system. Conclusion: The on‐line information system studied was less accurate for storing and retrieving information than a conventional ambulance file system. Thus, more technical development is needed before this on‐line system can be recommended for use in major incidents or disasters.

The authors describe the file management system of DRAGON SLAYER, a distributed operating system which provides transparent resource sharing in a heterogeneous local area network with completely decentralized control. Users are able to use any of the system files for which they have authorization, without regard to the individual characteristics of the computers on which the files reside or the physical locations of the users and files. In addition, files can be dynamically fragmented, and the fragments can be replicated and relocated dynamically. Copies are kept mutually consistent while all file operations work either transparently on the whole file or on specific fragments. The DRAGON SLAYER resource management supporting these file system operations is presented. Beyond the obvious advantages of file access reliability and flexibility, the authors present simulation results proving the superior performance of this file system as compared with conventional distributed file systems with non-fragmented files. >

This paper presents a novel distributed file system TLDFS, which consists of two layers. One is the block device layer, which makes the distributed file system manage the consistency of data easily by choosing an appropriate granularity of lock. We implement the distributed interfaces and the new data organization at the block level, which is different from most distributed file systems. The other is the file system layer that consists of three parts: interconnecting module, locking module and distributed file system module. Our prototype system proves the feasibility of the two-layered structure and the experiments show several advantages of TLDFS.

A cryptographic file system is the representative way of assuring confidentiality of files in operating systems. For secure embedded operating systems, the cryptographic file system could be a practical technique. In general, cryptographic file systems are implemented using a stackable file system or a device driver. These two mechanisms can provide user transparent encryption/decryption of cryptographic file systems. But these mechanisms sometimes encrypt or decrypt data redundantly or unnecessarily. Embedded systems with a low speed CPU and flash storage are more affected by the problems than general systems. We addressed the above mentioned problems by applying an encryption algorithm on buffer caches and enabling one buffer cache to have both encrypted and decrypted data together. Experimental results show that the proposed mechanisms reduce the redundant or unnecessary operations and it can improve the performance of cryptographic file systems.KeywordsSecurityCryptographic File SystemEmbedded Operating SystemBuffer CacheLinux

Analysis of real-time operating systems’ file systems: Built-in cameras from vehicles

Massively parallel applications often require periodic data checkpointing for program restart and post-run data analysis. Although high performance computing systems provide massive parallelism and computing power to fulfill the crucial requirements of the scientific applications, the I/O tasks of high-end applications do not scale. Strict data consistency semantics adopted from traditional file systems are inadequate for homogeneous parallel computing platforms. For high performance parallel applications independent I/O is critical, particularly if checkpointing data are dynamically created or irregularly partitioned. In particular, parallel programs generating a large number of unrelated I/O accesses on large-scale systems often face serious I/O serializations introduced by lock contention and conflicts at file system layer. As these applications may not be able to utilize the I/O optimizations requiring process synchronization, they pose a great challenge for parallel I/O architecture and software designs. We propose an I/O mechanism to bridge the gap between scientific applications and parallel storage systems. A static file domain partitioning method is developed to align the I/O requests and produce a client-server mapping that minimizes the file lock acquisition costs and eliminates the lock contention. Our performance evaluations of production application I/O kernels demonstrate scalable performance and achieve high I/O bandwidths.

Existing nonvolatile memory (NVM)-based file systems can fully leverage the characteristics of NVM to obtain better performance than traditional disk-based file systems. It has the potential capacity to efficiently manage metadata and perform fast metadata operations. However, most NVM-based file systems mainly focus on managing file metadata (inode), while pay little attention to directory metadata (dentry), which also has a noticeable impact on the file system performance. Besides, the traditional journaling technique that guarantees metadata consistency may not yield satisfactory performance on NVM-based file systems. To solve these problems, in this article we propose a fast and low overhead metadata operation mechanism, called FLOMO. It first adopts a novel slotted-paging structure in NVM to reorganize dentry for efficiently performing dentry operations, and utilizes the red–black tree in DRAM to accelerate dentry lookup and the search process of dentry deletion. Moreover, FLOMO presents a selective journaling scheme for metadata updates, which partially logs the changes related to dentry in the proposed slotted page, thereby, mitigating the redundant journaling overhead. To verify FLOMO, we implement it in a typical NVM-based file system, the persistent memory file system (PMFS). Experimental results show that FLOMO accelerates the metadata operations in PMFS by 34.4% <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 59$ </tex-math></inline-formula> %, and notably reduces the journaling overhead for metadata, shortening the latency by 59% on average. For real-world applications, FLOMO has higher throughput compared with PMFS, PMFS without journal, and NOVA, achieving up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.1\times $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\times $ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.3\times $ </tex-math></inline-formula> performance improvement, respectively.

Emerging byte-addressable non-volatile memory offers high performance as DRAM and data persistency like disks. In order to use the NVM in a reasonable manner, existing storage systems put the NVM on memory bus and design a specialized file system to take advantage of the characteristics of NVM. However, the current NVM-based file systems use the page table to provide direct access in NVM, which cause performance overhead in page fault. In this paper, to address this issue, we propose a unified mapping structure based memory-mapped file system. It combines the advantages of memory page table and file data index, and uses the page table structure based data index as the unified address structure. By using this method, we can efficiently implement the mapping and release of resources, also, we can effectively reduce the overhead of page fault. By using the memory simulator, we evaluate our file system in various workloads. Evaluation results show that, our unified mapping structure based memory-mapped file system effectively improves the access performance and reduces space overhead during the accessing process.

The performance of a network based computing system that consists of a number of clients and a server, interconnected by a local area network, is studied. Each client represents a diskless or swapful workstation, or an X terminal, and generates application workload using either a conventional UNIX file system or the Network File System (NFS). To characterize the application workload and the effect of the protocol (login, rlogin, NFS), the user interface (workstation, X terminal) and its configuration (memory size, disk storage), a series of measurement experiments was performed in a controlled environment. During each experiment the traffic on the network and the activity on the various system resources were monitored. The measurements obtained are used to parameterize a queuing network model of the system, which is then used to project the performance of the system under various load conditions, to identify system bottlenecks, and to compare design alternatives. >

The ARINC-653 standard, dictating the use of time and space partitioning in real-time avionics systems, has been widely embraced by the industry. We present the design of real-time file system (RTFS), a file system that complies with the ARINC-653 standard and the emerging standard for a file system for ARINC-653. RTFS provides realtime accesses to data stored on a variety of mass storage device. In addition to an interface complying with emerging standard, RTFS provides an application interface that complies with a subset of the POSIX standard. RTFS is implemented as a normal ARINC-653 partition. Task partitions communicate their file operation requests to RTFS via queuing ports; such ports are also used to deliver the responses from RTFS to the task partitions. The temporal behavior of RTFS is predictable and the response times for file operations are bounded. The design of RTFS handles a mix of hard and soft real-time file access requests. RTFS implements metadata journaling using on-board non-volatile memory devices to provide fast file updates and fast file system recovery on faults. Finally, RTFS includes facilities to support network-centric operations and a set of design and maintenance tools. This paper overviews the design of RTFS and describes the realization of the many unique features of RTFS.

Real-Time Executive for Multiprocessor Systems (RTEMS) is an open-source real-time operating system (RTOS) that is widely used in commercial and free embedded applications with notable adoption in space flight software and scientific instrument control for space science and high energy physics. RTEMS has rich support for POSIX environments and supports multiple POSIX and BSD file systems, along with some custom file systems designed specifically to meet the needs of real-time and embedded applications storage and retrieval of data. The range of file systems available in RTEMS motivates this study that investigates the salient features of each file system to help identify strengths and weaknesses with respect to application requirements and constraints. In this paper, we provide a comparison of the available RTEMS file systems and present some performance benchmarking results.

The problem of scheduling disk requests in a personal hard real-time read/write file system is examined. We propose a fixed-period scan (FSCAN) approach for disk scheduling in our file system. The idea is to use the CSCAN policy to pick up the data blocks requested by a periodic preemptive schedule. The approach trades disk block size and memory buffer size for higher performance. We derive the worst-case seek and rotational overhead for the FSCAN algorithm, and we show that the worst case seek overhead can be measured empirically for a large class of seek functions. Using this approach and utilizing measured seek functions from real disk drives, we show that these policies can transfer data at 40-70% of the maximum transfer rate of modern disk drives, depending an the file system parameters. A configuration program is developed to automatically test and configure the FSCAN algorithm for modern hard disks. The design and testing of this program are described.

Parallel file systems (PFS) are used to distribute data processing and establish shared access to large-scale data. Despite being able to provide high I/O bandwidth on each node, PFS has difficulty utilizing the I/O bandwidth due to a single connection between the client and server nodes. To mitigate the performance bottleneck, users increase the number of connections between the nodes by modifying PFS or applications. However, it is difficult to modify PFS itself due to its complicated internal structure. Thus, PFS users manually increase the number of connections between the nodes by employing several methods. In this paper, we propose a user-transparent I/O subsystem, MulConn, to make users exploit high I/O bandwidth between nodes. To avoid the modifications of PFS and user applications, we have developed a horizontal mount procedure and two I/O scheduling policies, TtoS and TtoM, in the virtual file system (VFS) layer. We expose a single mount point that has multiple connections by modifying the mount path of VFS from vertical hierarchy to horizontal hierarchy. We also introduce two I/O scheduling policies to distribute I/O requests evenly to multiple connections. The experimental results show that MulConn improves write and read performance by up to 2.6x and 2.8x, respectively, compared with those of PFS using the existing kernel. In addition, we provide the best I/O performance that PFS can provide in the given experimental environments.

Computational scientists must understand results from experimental, observational and computational simulation generated data to gain insights and perform knowledge discovery. As systems approach the petascale range, problems that were unimaginable a few years ago are within reach. With the increasing volume and complexity of data produced by ultra-scale simulations and high-throughput experiments, understanding the science is largely hampered by the lack of comprehensive I/O, storage, acceleration of data manipulation, analysis, and mining tools. Scientists require techniques, tools and infrastructure to facilitate better understanding of their data, in particular the ability to effectively perform complex data analysis, statistical analysis and knowledge discovery. The goal of this work is to enable more effective analysis of scientific datasets through the integration of enhancements in the I/O stack, from active storage support at the file system layer to MPI-IO and high-level I/O library layers. We propose to provide software components to accelerate data analytics, mining, I/O, and knowledge discovery for large-scale scientific applications, thereby increasing productivity of both scientists and the systems. Our approaches include 1) design the interfaces in high-level I/O libraries, such as parallel netCDF, for applications to activate data mining operations at the lower I/O layers; 2) Enhance MPI-IO runtime systems to incorporate the functionality developed as a part of the runtime system design; 3) Develop parallel data mining programs as part of runtime library for server-side file system in PVFS file system; and 4) Prototype an active storage cluster, which will utilize multicore CPUs, GPUs, and FPGAs to carry out the data mining workload.

In this project, we propose an enhancement and analysis of transport control protocol friendly rate control (TFRC) for real-time data application (audio/video). Traditionally, real-time data transmission has been accomplished over the user datagram protocol (UDP). The challenging issues of using transport control protocol (TCP) are restrictive bandwidth and lagging. Additionally, it is widely known that TCP is ill-suited to real-time multimedia streaming application. Having known these issues, this project aims to study the possibilities for analysis and improvement of real-time data application using TFRC which is designed for long-lived streams. As known, there are many advantages of TFRC, which are congestion control and guaranteeing the required throughput. Therefore, this project explores and proposes the advantages of TFRC in transmitting and receiving real-time data which currently uses UDP. It is proposed that the investigation of TFRC in real-time data is conducted using simulation technique. During the simulation, the developed model is representing the real-time application for analyzing the performance of modified TFRC. The simulation study of this project is to analyze and evaluate some of restraint issues for real-time data application to use TFRC. As a solution, a few suggestions are discussed to overcome stated problem and make comparison and evaluation, which are aimed to get results about better performance between enhanced TFRC and UDP in terms of streaming real-time data.