Current File Systems Research Articles

Apically extruded debris of different file systems used with various kinematic movements during retreatment: An in vitro study.

This study aimed to examine the amount of apically extruded debris and time during retreatment with five current file systems, which exhibit various kinematic movements. One hundred upper central incisors were shaped with manual files and filled using the thermoplastic injection method. The root canal fillings in each group (n=20) were removed using the Genius (GN), ProTaper Next (PTN), Reciproc (RCP) Blue, Tango-Endo (TE) and Twisted File Adaptive (TFA) file systems. The apically extruded debris was collected in preweighed Eppendorf tubes. Time to reach working length and total time were also recorded. The PTN, RCP Blue and TFA instruments caused significantly less apically extruded debris and shorter total retreatment time than the GN and TE file systems (p < 0.05). The time to reach the working length was the shortest in the PTN group compared to the other groups (p < 0.05). All file systems extruded debris while removing the root canal filling.

An End-to-End Learning-Based Metadata Management Approach for Distributed File Systems

Current distributed file systems are designed to support PB-scale even EB-scale data storage. Metadata service, which manages file attribute information and the global namespace tree, is crucial to system performance. Distributed metadata management, using multiple metadata servers (MDS's) to store metadata, provides effective approaches to alleviate the workload of a single server. However, maintaining good metadata locality and keeping load balancing among MDS's is a nontrivial problem. In this paper, we present the first machine learning based model called DeepHash, which leverages the neural network to learn a locality preserving hashing (LPH) mapping scheme. DeepHash first converts the metadata nodes to feature vectors by the network embedding technology. Due to the absence of training labels, i.e., the hash values of metadata nodes, we design a pair loss function with distinctive characters to train DeepHash, and introduce the sampling strategy to improve the training efficiency. Besides, we propose an efficient algorithm to dynamically balance the workload and adopt the cache model to improve query efficiency. The experiments on the Amazon EC2 platform demonstrate that the DeepHash can preserve the metadata locality meanwhile maintaining a high load balancing, which denotes the effectiveness and efficiency of DeepHash compared with traditional and state-of-the-art schemes.

Reverse engineering of ReFS

File system forensics is an important part of Digital Forensics. Investigators of storage media have traditionally focused on the most commonly used file systems such as NTFS, FAT, ExFAT, Ext2-4, HFS+, APFS, etc. NTFS is the current file system used by Windows for the system volume, but this may change in the future. In this paper we will show the structure of the Resilient File System (ReFS), which has been available since Windows Server 2012 and Windows 8. The main purpose of ReFS is to be used on storage spaces in server systems, but it can also be used in Windows 8 or newer. Although ReFS is not the current standard file system in Windows, while users have the option to create ReFS file systems, digital forensic investigators need to investigate the file systems identified on a seized media. Further, we will focus on remnants of non-allocated metadata structures or attributes. This may allow metadata carving, which means searching for specific attributes that are not allocated. Attributes found can then be used for file recovery. ReFS uses superblocks and checkpoints in addition to a VBR, which is different from other Windows file systems. If the partition is reformatted with another file system, the backup superblocks can be used for partition recovery. Further, it is possible to search for checkpoints in order to recover both metadata and content.Another concept not seen for Windows file systems, is the sharing of blocks. When a file is copied, both the original and the new file will share the same content blocks. If the user changes the copy, new data runs will be created for the modified content, but unchanged blocks remain shared. This may impact file carving, because part of the blocks previously used by a deleted file might still be in use by another file. The large default cluster size, 64 KiB, in ReFS v1.2 is an advantage when carving for deleted files, since most deleted files are less than 64 KiB and therefore only use a single cluster. For ReFS v3.2 this advantage has decreased because the standard cluster size is 4 KiB.Preliminary support for ReFS v1.2 has been available in EnCase 7 and 8, but the implementation has not been documented or peer-reviewed. The same is true for Paragon Software, which recently added ReFS support to their forensic product. Our work documents how ReFS v1.2 and ReFS v3.2 are structured at an abstraction level that allows digital forensic investigation of this new file system. At the time of writing this paper, Paragon Software is the only digital forensic tool that supports ReFS v3.x.It is the most recent version of the ReFS file system that is most relevant for digital forensics, as Windows automatically updates the file system to the latest version on mount. This is why we have included information about ReFS v3.2. However, it is possible to change a registry value to avoid updating. The latest ReFS version observed is 3.4, but the information presented about 3.2 is still valid. In any criminal case, the investigator needs to investigate the file system version found.

A distributed data management system to support large-scale data analysis

Distributed data management is a key technology to enable efficient massive data processing and analysis in cluster-computing environments. Specifically, in environments where the data volumes are beyond the system capabilities, big data files are required to be summarized by representative samples with the same statistical properties as the whole dataset. This paper proposes a big data management system (BDMS) based on distributed random sample data blocks. It presents a high-level architecture design of the BDMS which extends the current distributed file systems. This system offers certain functionalities for block-level management such as statistically-aware data partitioning, data blocks organization, and data blocks selection. This paper also presents a round-random partitioning scheme to represent a big dataset as a set of non-overlapping data blocks; each block is a random sample of the whole dataset. Based on the presented scheme, two algorithms are introduced as an implementation strategy to convert the HDFS blocks of a big file into a set of random sample data blocks which is also stored in HDFS. The experimental results show that the execution time of partitioning operation is acceptable in the real applications because this operation is only performed once on each input data file.

A multi‐channel architecture for metadata management in cloud storage systems by binding CPU‐cores to disks

SummaryMetadata operations have become dominant file operations in the storage systems. In the scenarios of read‐more and write‐less of massive small files, the current distributed file systems suffer from the unsatisfying performance and scalability of metadata service because of random disk I/O during metadata operations. In this paper, a highly efficient metadata management architecture for cloud storage systems is proposed. The cluster design significantly improves the scalability of the system. A concept of the disk I/O channel is introduced, which is an independent data storage pipe by binding an independent CPU‐core to each physical disk. In addition, a multi‐channel fast key‐value storage engine is proposed to provide the extremely efficient performance for the underlying storage service, which takes full advantages of multi‐core processors and parallel disks I/O. Besides, a new dynamic load‐balancing strategy is proposed to reduce load thrashing and improve the precision of rebalancing among the clusters. Performance measurements under a variety of benchmarks show that the metadata management is capable of handling the massive small files storage and the performance is improved significantly compared to the existing solutions. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Using IKAROS as a data transfer and management utility within the KM3NeT computing model

KM3NeT is a future European deep-sea research infrastructure hosting a new generation neutrino detectors that - located at the bottom of the Mediterranean Sea - will open a new window on the universe and answer fundamental questions both in particle physics and astrophysics. IKAROS is a framework that enables creating scalable storage formations on-demand and helps addressing several limitations that the current file systems face when dealing with very large scale infrastructures. It enables creating ad-hoc nearby storage formations and can use a huge number of I/O nodes in order to increase the available bandwidth (I/O and network). IKAROS unifies remote and local access in the overall data flow, by permitting direct access to each I/O node. In this way we can handle the overall data flow at the network layer, limiting the interaction with the operating system. This approach allows virtually connecting, at the users level, the several different computing facilities used (Grids, Clouds, HPCs, Data Centers, Local computing Clusters and personal storage devices), on-demand, based on the needs, by using well known standards and protocols, like HTTP.

BetrFS

The B ε -tree File System , or B e trFS (pronounced “better eff ess”), is the first in-kernel file system to use a write-optimized data structure (WODS). WODS are promising building blocks for storage systems because they support both microwrites and large scans efficiently. Previous WODS-based file systems have shown promise but have been hampered in several ways, which B e trFS mitigates or eliminates altogether. For example, previous WODS-based file systems were implemented in user space using FUSE, which superimposes many reads on a write-intensive workload, reducing the effectiveness of the WODS. This article also contributes several techniques for exploiting write-optimization within existing kernel infrastructure. B e trFS dramatically improves performance of certain types of large scans, such as recursive directory traversals, as well as performance of arbitrary microdata operations, such as file creates, metadata updates, and small writes to files. B e trFS can make small, random updates within a large file 2 orders of magnitude faster than other local file systems. B e trFS is an ongoing prototype effort and requires additional data-structure tuning to match current general-purpose file systems on some operations, including deletes, directory renames, and large sequential writes. Nonetheless, many applications realize significant performance improvements on B e trFS. For instance, an in-place rsync of the Linux kernel source sees roughly 1.6--22 × speedup over commodity file systems.

Improving file system performance and reliability of car digital video recorders

Car digital video recorders (DVRs) store realtime audio/video data at flash memory storage device. Car DVR should handle a large amount of high quality multimedia data with high reliability. However, current file systems are vulnerable to sudden-power-offs and flash memory errors. This paper proposes flash-aware cluster allocation techniques and a flash-aware journaling technique. The flash-aware cluster allocation techniques can reduce the probability of file system corruptions and file fragmentations. The flash-aware journaling technique can ensure the file system consistency without significant overheads. Experiments on a simulator and a real system showed that the proposed techniques can prevent file fragmentations and file system corruptions, and they can improve the write performance and lifetime of SD card significantly.

Protecting data in cloud environment with attribute-based encryption

Traditional file systems cannot satisfy the recent requirements in the cloud environment. Meanwhile, current file systems designed for cloud computing cannot provide enough flexibility, fine-grained access control and access security. In this paper, a novel secure file sharing scheme based on attribute control is presented. In order to design a practical cloud file system with attribute based encryption, we give a systematic definition of attribute computing in cloud computing environment. Based on the definition, we present a secure and practical attribute based encryption scheme without pairings CP-ABE-WP under cloud computing scenarios. Then we design a secure cloud file system applying our CP-ABE-WP to provide data management and secure data sharing. According to our analysis and test, the scheme is chosen plaintext secure in selective ID model with acceptable performance and can satisfy the file sharing application in cloud computing.

File systems deserve verification too!

File systems are too important, and current ones are too buggy, to remain unverified. Yet the most successful verification methods for functional correctness remain too expensive for current file system implementations-we need verified correctness but at reasonable cost. This paper presents our vision and ongoing work to achieve this goal for a new high-performance flash file system, called BilbyFs. BilbyFs is carefully designed to be highly modular, so it can be verified against a high-level functional specification one component at a time. This modular implementation is captured in a set of domain specific languages from which we produce the design-level specification, as well as its optimised C implementation. Importantly, we also automatically generate the proof linking these two artefacts. The combination of these features dramatically reduces verification effort. Verified file systems are now within reach for the first time.

The self-adjusting file (SAF) system: An evidence-based update

Current rotary file systems are effective tools. Nevertheless, they have two main shortcomings: They are unable to effectively clean and shape oval canals and depend too much on the irrigant to do the cleaning, which is an unrealistic illusionThey may jeopardize the long-term survival of the tooth via unnecessary, excessive removal of sound dentin and creation of micro-cracks in the remaining root dentin. The new Self-adjusting File (SAF) technology uses a hollow, compressible NiTi file, with no central metal core, through which a continuous flow of irrigant is provided throughout the procedure. The SAF technology allows for effective cleaning of all root canals including oval canals, thus allowing for the effective disinfection and obturation of all canal morphologies. This technology uses a new concept of cleaning and shaping in which a uniform layer of dentin is removed from around the entire perimeter of the root canal, thus avoiding unnecessary excessive removal of sound dentin. Furthermore, the mode of action used by this file system does not apply the machining of all root canals to a circular bore, as do all other rotary file systems, and does not cause micro-cracks in the remaining root dentin. The new SAF technology allows for a new concept in cleaning and shaping root canals: Minimally Invasive 3D Endodontics.

리눅스에서 Iozone 도구를 이용한 저널링 파일 시스템 성능 평가 : read, write 중심으로

If a file system is damaged because of the unusual system close, the system performs the consistency test using fsch and it takes long time. Especially, if it is a big file system, it will take a lot of time. The journaling file system that uses journaling technique, can reduce the restoring time because it uses meta data and it may increase the chance of restoration when restoring. The goal of this paper compared performance evaluation journaling file systems focused on the reading and writing using Iozone tool which is the kernel based benchmarking tool in linux operating system. In this paper, Ex4 which is the current basic Linux file system. is 1.28x faster than XFS file system in terms of file read performance and 1.22x faster than Ext3 file system in terms of file write performance.

A Novel PIM System and its Effective Storage Compression Scheme

The increasingly large amount of personal information poses a critical problem to users. Traditional file organization in hierarchical directories is not suited to the effective management of personal information. In order to overcome the shortcomings of the current hierarchical file system and efficiently organize and maintain personal information, some new tools are expected to be invented. In this paper, we propose a novel scheme called concept space - a network of concepts and their associations – and use topic map as the underlying data model. We present a materialized view scheme to provide users with a flexible view of the file system according to their own cognition. We also reduce the storage requirement to save space usage of this system by borrowing some ideas from XML data management and contriving a novel and efficient data compression scheme. To demonstrate the effectiveness of the above idea, we have implemented a prototype personal information management system called NovaPIM and presented its system architecture. Extensive experiments show that our proposed scheme is both efficient and effective.

The Self-adjusting File (SAF). Part 1: Respecting the Root Canal Anatomy—A New Concept of Endodontic Files and Its Implementation

AimTo introduce a new concept, the self-adjusting file (SAF), and discuss its unique features compared with current rotary nickel-titanium file systems. The New ConceptThe SAF file is hollow and designed as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root canal. A single file is used throughout the procedure. It is inserted into a path initially prepared by a # 20 K-file and operated with a transline- (in-and-out) vibration. The resulting circumferential pressure allows the file's abrasive surface to gradually remove a thin uniform hard-tissue layer from the entire root canal surface, resulting in a canal with a similar cross-section but of larger dimensions. This holds also for canals with an oval or flat cross-section, which will be enlarged to a flat or oval cross-section of larger dimensions. The straightening of curved canals is also reduced because of the high pliability of the file and the absence of a rigid metal core. Thus, the original shape of the root canal is respected both longitudinally and in cross-section. The hollow SAF file is operated with a constant flow of irrigant that enters the full length of the canal and that is activated by the vibration and is replaced continuously throughout the procedure. This results in effective cleaning even at the cul de sac apical part of the canal. The SAF has high mechanical endurance; file separation does not occur; and mechanical failure, if it occurs, is limited to small tears in the latticework. ConclusionThe SAF represents a new step forward in endodontic file development that may overcome many of the shortcomings of current rotary nickel-titanium file systems.

FRASH

In this work, we develop a novel hybrid file system, FRASH, for storage-class memory and NAND Flash. Despite the promising physical characteristics of storage-class memory, its scale is an order of magnitude smaller than the current storage device scale. This fact makes it less than desirable for use as an independent storage device. We carefully analyze in-memory and on-disk file system objects in a log-structured file system, and exploit memory and storage aspects of the storage-class memory to overcome the drawbacks of the current log-structured file system. FRASH provides a hybrid view storage-class memory. It harbors an in-memory data structure as well as a on-disk structure. It provides nonvolatility to key data structures which have been maintained in-memory in a legacy log-structured file system. This approach greatly improves the mount latency and effectively resolves the robustness issue. By maintaining on-disk structure in storage-class memory, FRASH provides byte-addressability to the file system object and metadata for page, and subsequently greatly improves the I/O performance compared to the legacy log-structured approach. While storage-class memory offers byte granularity, it is still far slower than its DRAM counter part. We develop a copy-on-mount technique to overcome the access latency difference between main memory and storage-class memory. Our file system was able to reduce the mount time by 92% and file system I/O performance was increased by 16%.

Design and Implementation of a Group Key Server-Based Cryptographic File System

Network storage techniques facilitate data sharing but also introduce new vulnerabilities. Cryptographic file systems provide the confidentiality and integrity of file data stored on servers that are not under users′ direct control by cryptographic methods. The key management schemes for current shared cryptographic file systems cannot satisfy the security, flexibility and efficiency requirements simultaneously. This paper proposes a cryptographic file system called CKS-CFS. A trusted Group Key Server (GKS) is introduced to manage file encryption keys in a centralized manner and to enable the employment of flexible access control policies. The computation and storage requirement for GKS is reduced through the use of access control blocks and lockboxes so that the function of GKS can be implemented by hardware to provide strong security. The overhead of revocation is reduced by block granularity encryption and key versioning technique. The authors have implemented a prototype of GKS-CFS based on Luster and evaluated its performance. Compared with other systems, the cryptographic cost in common file operations in GKS-CFS is reduced by an order of magnitude by avoiding the usage of public-key cryptography; Bonnie++ benchmark test shows that the performance of sequential read/write and random file operations are reduced on average by 42.0% and 8.4% respectively.

IBM Scale out File Services: Reinventing network-attached storage

This paper focuses on the challenges of creating a scalable network-attached storage (NAS) filer with hundreds of nodes on top of the IBM General Parallel File System™ (GPFS™). The filer is created as a multiheaded data exporter over Ethernet and uses the Common Internet File System (CIFS) as implemented by the Samba open-source project and a Network File System (NFS) protocol server. Special focus is given to ensure the consistency of data in an efficient manner for applications that have complex access patterns from a large number of nodes. Also considered are the challenges of providing an extremely high-performance facility for exporting data in parallel and the demands of storing very large amounts of data. Introducing new aspects of storage management--such as storage pools and fle sets as they are implemented in current file systems--into NAS appliances enables the management of large amounts of data in a single namespace.

A Conversation with Jeff Bonwick and Bill Moore

This month ACM Queue speaks with two Sun engineers who are bringing file systems into the 21st century. Jeff Bonwick, CTO for storage at Sun, led development of the ZFS file system, which is now part of Solaris. Bonwick and his co-lead, Sun Distinguished Engineer Bill Moore, developed ZFS to address many of the problems they saw with current file systems, such as data integrity, scalability, and administration. In our discussion this month, Bonwick and Moore elaborate on these points and what makes ZFS such a big leap forward.

An Architecture for High Performance File SystemI/O

This paper presents an architecture of current filesystem implementations as well as our new filesystem SpadFS and operating system Spad with rewritten VFS layer targeted at high performance I/O applications. The paper presents microbenchmarks and real-world benchmarks of different filesystems on the same kernel as well as benchmarks of the same filesystem on different kernels — enabling the reader to make conclusion how much is the performance of various tasks affected by operating system and how much by physical layout of data on disk. The paper describes our novel features — most notably continuous allocation of directories and cross-file readahead — and shows their impact on performance. Keywords— Filesystem, operating system, VFS, performance, readahead

Towards building a conflict‐free mobile distributed file system

AbstractThe rising demand for mobile computing has created a need for an improved file system that supports mobile clients. Current file systems with support for mobility provide availability through file replicas that are cached at the client side. However, mobile clients may experience different obstacles with regards to the local cache, such as the limited network bandwidth, the intermittent connection, and serious conflicts when synchronizing back to the server. In this paper, we propose a novel mobile distributed file system design, which provides high availability and reliable storage for files and guarantees that file operations are executed regardless of concurrency and failure issues. The design is intended to fit mobile clients (e.g. PDAs and cell phones) that have limited storage space and cannot store all of the data they need, and yet require access to these data at all times. We adopt a server‐side caching in order to guarantee sufficient caching space to all mobile clients, and to ensure the availability of files in the case of clients' failures. We present our algorithm, describe its implementation, simulate its high availability functions, and report on its performance evaluation using a cluster of workstations. Our simulation results indicate clearly that our algorithm exhibits a significant degree of automation and conflict‐free mobile file system. Copyright © 2007 John Wiley &amp; Sons, Ltd.