Virtual File System and Devices
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Copy on Write Based File Systems Performance Analysis and Implementation
Copy On Write Based File Systems Performance Analysis And Implementation Sakis Kasampalis Kongens Lyngby 2010 IMM-MSC-2010-63 Technical University of Denmark Department Of Informatics Building 321, DK-2800 Kongens Lyngby, Denmark Phone +45 45253351, Fax +45 45882673 [email protected] www.imm.dtu.dk Abstract In this work I am focusing on Copy On Write based file systems. Copy On Write is used on modern file systems for providing (1) metadata and data consistency using transactional semantics, (2) cheap and instant backups using snapshots and clones. This thesis is divided into two main parts. The first part focuses on the design and performance of Copy On Write based file systems. Recent efforts aiming at creating a Copy On Write based file system are ZFS, Btrfs, ext3cow, Hammer, and LLFS. My work focuses only on ZFS and Btrfs, since they support the most advanced features. The main goals of ZFS and Btrfs are to offer a scalable, fault tolerant, and easy to administrate file system. I evaluate the performance and scalability of ZFS and Btrfs. The evaluation includes studying their design and testing their performance and scalability against a set of recommended file system benchmarks. Most computers are already based on multi-core and multiple processor architec- tures. Because of that, the need for using concurrent programming models has increased. Transactions can be very helpful for supporting concurrent program- ming models, which ensure that system updates are consistent. Unfortunately, the majority of operating systems and file systems either do not support trans- actions at all, or they simply do not expose them to the users. -
The Linux Kernel Module Programming Guide
The Linux Kernel Module Programming Guide Peter Jay Salzman Michael Burian Ori Pomerantz Copyright © 2001 Peter Jay Salzman 2007−05−18 ver 2.6.4 The Linux Kernel Module Programming Guide is a free book; you may reproduce and/or modify it under the terms of the Open Software License, version 1.1. You can obtain a copy of this license at http://opensource.org/licenses/osl.php. This book is distributed in the hope it will be useful, but without any warranty, without even the implied warranty of merchantability or fitness for a particular purpose. The author encourages wide distribution of this book for personal or commercial use, provided the above copyright notice remains intact and the method adheres to the provisions of the Open Software License. In summary, you may copy and distribute this book free of charge or for a profit. No explicit permission is required from the author for reproduction of this book in any medium, physical or electronic. Derivative works and translations of this document must be placed under the Open Software License, and the original copyright notice must remain intact. If you have contributed new material to this book, you must make the material and source code available for your revisions. Please make revisions and updates available directly to the document maintainer, Peter Jay Salzman <[email protected]>. This will allow for the merging of updates and provide consistent revisions to the Linux community. If you publish or distribute this book commercially, donations, royalties, and/or printed copies are greatly appreciated by the author and the Linux Documentation Project (LDP). -
File Systems and Disk Layout I/O: the Big Picture
File Systems and Disk Layout I/O: The Big Picture Processor interrupts Cache Memory Bus I/O Bridge Main I/O Bus Memory Disk Graphics Network Controller Controller Interface Disk Disk Graphics Network 1 Rotational Media Track Sector Arm Cylinder Platter Head Access time = seek time + rotational delay + transfer time seek time = 5-15 milliseconds to move the disk arm and settle on a cylinder rotational delay = 8 milliseconds for full rotation at 7200 RPM: average delay = 4 ms transfer time = 1 millisecond for an 8KB block at 8 MB/s Bandwidth utilization is less than 50% for any noncontiguous access at a block grain. Disks and Drivers Disk hardware and driver software provide basic facilities for nonvolatile secondary storage (block devices). 1. OS views the block devices as a collection of volumes. A logical volume may be a partition ofasinglediskora concatenation of multiple physical disks (e.g., RAID). 2. OS accesses each volume as an array of fixed-size sectors. Identify sector (or block) by unique (volumeID, sector ID). Read/write operations DMA data to/from physical memory. 3. Device interrupts OS on I/O completion. ISR wakes up process, updates internal records, etc. 2 Using Disk Storage Typical operating systems use disks in three different ways: 1. System calls allow user programs to access a “raw” disk. Unix: special device file identifies volume directly. Any process that can open thedevicefilecanreadorwriteany specific sector in the disk volume. 2. OS uses disk as backing storage for virtual memory. OS manages volume transparently as an “overflow area” for VM contents that do not “fit” in physical memory. -
Ext4 File System and Crash Consistency
1 Ext4 file system and crash consistency Changwoo Min 2 Summary of last lectures • Tools: building, exploring, and debugging Linux kernel • Core kernel infrastructure • Process management & scheduling • Interrupt & interrupt handler • Kernel synchronization • Memory management • Virtual file system • Page cache and page fault 3 Today: ext4 file system and crash consistency • File system in Linux kernel • Design considerations of a file system • History of file system • On-disk structure of Ext4 • File operations • Crash consistency 4 File system in Linux kernel User space application (ex: cp) User-space Syscalls: open, read, write, etc. Kernel-space VFS: Virtual File System Filesystems ext4 FAT32 JFFS2 Block layer Hardware Embedded Hard disk USB drive flash 5 What is a file system fundamentally? int main(int argc, char *argv[]) { int fd; char buffer[4096]; struct stat_buf; DIR *dir; struct dirent *entry; /* 1. Path name -> inode mapping */ fd = open("/home/lkp/hello.c" , O_RDONLY); /* 2. File offset -> disk block address mapping */ pread(fd, buffer, sizeof(buffer), 0); /* 3. File meta data operation */ fstat(fd, &stat_buf); printf("file size = %d\n", stat_buf.st_size); /* 4. Directory operation */ dir = opendir("/home"); entry = readdir(dir); printf("dir = %s\n", entry->d_name); return 0; } 6 Why do we care EXT4 file system? • Most widely-deployed file system • Default file system of major Linux distributions • File system used in Google data center • Default file system of Android kernel • Follows the traditional file system design 7 History of file system design 8 UFS (Unix File System) • The original UNIX file system • Design by Dennis Ritche and Ken Thompson (1974) • The first Linux file system (ext) and Minix FS has a similar layout 9 UFS (Unix File System) • Performance problem of UFS (and the first Linux file system) • Especially, long seek time between an inode and data block 10 FFS (Fast File System) • The file system of BSD UNIX • Designed by Marshall Kirk McKusick, et al. -
Devicelock® DLP 8.3 User Manual
DeviceLock® DLP 8.3 User Manual © 1996-2020 DeviceLock, Inc. All Rights Reserved. Information in this document is subject to change without notice. No part of this document may be reproduced or transmitted in any form or by any means for any purpose other than the purchaser’s personal use without the prior written permission of DeviceLock, Inc. Trademarks DeviceLock and the DeviceLock logo are registered trademarks of DeviceLock, Inc. All other product names, service marks, and trademarks mentioned herein are trademarks of their respective owners. DeviceLock DLP - User Manual Software version: 8.3 Updated: March 2020 Contents About This Manual . .8 Conventions . 8 DeviceLock Overview . .9 General Information . 9 Managed Access Control . 13 DeviceLock Service for Mac . 17 DeviceLock Content Security Server . 18 How Search Server Works . 18 ContentLock and NetworkLock . 20 ContentLock and NetworkLock Licensing . 24 Basic Security Rules . 25 Installing DeviceLock . .26 System Requirements . 26 Deploying DeviceLock Service for Windows . 30 Interactive Installation . 30 Unattended Installation . 35 Installation via Microsoft Systems Management Server . 36 Installation via DeviceLock Management Console . 36 Installation via DeviceLock Enterprise Manager . 37 Installation via Group Policy . 38 Installation via DeviceLock Enterprise Server . 44 Deploying DeviceLock Service for Mac . 45 Interactive Installation . 45 Command Line Utility . 47 Unattended Installation . 48 Installing Management Consoles . 49 Installing DeviceLock Enterprise Server . 52 Installation Steps . 52 Installing and Accessing DeviceLock WebConsole . 65 Prepare for Installation . 65 Install the DeviceLock WebConsole . 66 Access the DeviceLock WebConsole . 67 Installing DeviceLock Content Security Server . 68 Prepare to Install . 68 Start Installation . 70 Perform Configuration and Complete Installation . 71 DeviceLock Consoles and Tools . -
The Linux Device File-System
The Linux Device File-System Richard Gooch EMC Corporation [email protected] Abstract 1 Introduction All Unix systems provide access to hardware via de- vice drivers. These drivers need to provide entry points for user-space applications and system tools to access the hardware. Following the \everything is a file” philosophy of Unix, these entry points are ex- posed in the file name-space, and are called \device The Device File-System (devfs) provides a power- special files” or \device nodes". ful new device management mechanism for Linux. Unlike other existing and proposed device manage- This paper discusses how these device nodes are cre- ment schemes, it is powerful, flexible, scalable and ated and managed in conventional Unix systems and efficient. the limitations this scheme imposes. An alternative mechanism is then presented. It is an alternative to conventional disc-based char- acter and block special devices. Kernel device drivers can register devices by name rather than de- vice numbers, and these device entries will appear in the file-system automatically. 1.1 Device numbers Devfs provides an immediate benefit to system ad- ministrators, as it implements a device naming scheme which is more convenient for large systems Conventional Unix systems have the concept of a (providing a topology-based name-space) and small \device number". Each instance of a driver and systems (via a device-class based name-space) alike. hardware component is assigned a unique device number. Within the kernel, this device number is Device driver authors can benefit from devfs by used to refer to the hardware and driver instance. -
How UNIX Organizes and Accesses Files on Disk Why File Systems
UNIX File Systems How UNIX Organizes and Accesses Files on Disk Why File Systems • File system is a service which supports an abstract representation of the secondary storage to the OS • A file system organizes data logically for random access by the OS. • A virtual file system provides the interface between the data representation by the kernel to the user process and the data presentation to the kernel in memory. The file and directory system cache. • Because of the performance disparity between disk and CPU/memory, file system performance is the paramount issue for any OS Main memory vs. Secondary storage • Small (MB/GB) Large (GB/TB) • Expensive Cheap -2 -3 • Fast (10-6/10-7 sec) Slow (10 /10 sec) • Volatile Persistent Cannot be directly accessed • Directly accessible by CPU by CPU – Interface: (virtual) memory – Data should be first address brought into the main memory Secondary storage (disk) • A number of disks directly attached to the computer • Network attached disks accessible through a fast network - Storage Area Network (SAN) • Simple disks (IDE, SATA) have a described disk geometry. Sector size is the minimum read/write unit of data (usually 512Bytes) – Access: (#surface, #track, #sector) • Smart disks (SCSI, SAN, NAS) hide the internal disk layout using a controller type function – Access: (#sector) • Moving arm assembly (Seek) is expensive – Sequential access is x100 times faster than the random access Internal disk structure • Disk structure User Process Accessing Data • Given the file name. Get to the file’s FCB using the file system catalog (Open, Close, Set_Attribute) • The catalog maps a file name to the FCB – Checks permissions • file_handle=open(file_name): – search the catalog and bring FCB into the memory – UNIX: in-memory FCB: in-core i-node • Use the FCB to get to the desired offset within the file data: (CREATE, DELETE, SEEK, TRUNCATE) • close(file_handle): release FCB from memory Catalog Organization (Directories) • In UNIX, special files (not special device files) called directories contain information about other files. -
High Velocity Kernel File Systems with Bento
High Velocity Kernel File Systems with Bento Samantha Miller, Kaiyuan Zhang, Mengqi Chen, and Ryan Jennings, University of Washington; Ang Chen, Rice University; Danyang Zhuo, Duke University; Thomas Anderson, University of Washington https://www.usenix.org/conference/fast21/presentation/miller This paper is included in the Proceedings of the 19th USENIX Conference on File and Storage Technologies. February 23–25, 2021 978-1-939133-20-5 Open access to the Proceedings of the 19th USENIX Conference on File and Storage Technologies is sponsored by USENIX. High Velocity Kernel File Systems with Bento Samantha Miller Kaiyuan Zhang Mengqi Chen Ryan Jennings Ang Chen‡ Danyang Zhuo† Thomas Anderson University of Washington †Duke University ‡Rice University Abstract kernel-level debuggers and kernel testing frameworks makes this worse. The restricted and different kernel programming High development velocity is critical for modern systems. environment also limits the number of trained developers. This is especially true for Linux file systems which are seeing Finally, upgrading a kernel module requires either rebooting increased pressure from new storage devices and new demands the machine or restarting the relevant module, either way on storage systems. However, high velocity Linux kernel rendering the machine unavailable during the upgrade. In the development is challenging due to the ease of introducing cloud setting, this forces kernel upgrades to be batched to meet bugs, the difficulty of testing and debugging, and the lack of cloud-level availability goals. support for redeployment without service disruption. Existing Slow development cycles are a particular problem for file approaches to high-velocity development of file systems for systems. -
Deviceinstaller User Guide
Device Installer User Guide Part Number 900-325 Revision C 03/18 Table of Contents 1. Overview ...................................................................................................................................... 1 2. Devices ........................................................................................................................................ 2 Choose the Network Adapter for Communication ....................................................................... 2 Search for All Devices on the Network ........................................................................................ 2 Change Views .............................................................................................................................. 2 Add a Device to the List ............................................................................................................... 3 View Device Details ..................................................................................................................... 3 Device Lists ................................................................................................................................. 3 Save the Device List ................................................................................................................ 3 Open the Device List ............................................................................................................... 4 Print the Device List ................................................................................................................ -
Oracle® Linux 7 Managing File Systems
Oracle® Linux 7 Managing File Systems F32760-07 August 2021 Oracle Legal Notices Copyright © 2020, 2021, Oracle and/or its affiliates. This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, then the following notice is applicable: U.S. GOVERNMENT END USERS: Oracle programs (including any operating system, integrated software, any programs embedded, installed or activated on delivered hardware, and modifications of such programs) and Oracle computer documentation or other Oracle data delivered to or accessed by U.S. Government end users are "commercial computer software" or "commercial computer software documentation" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, the use, reproduction, duplication, release, display, disclosure, modification, preparation of derivative works, and/or adaptation of i) Oracle programs (including any operating system, integrated software, any programs embedded, installed or activated on delivered hardware, and modifications of such programs), ii) Oracle computer documentation and/or iii) other Oracle data, is subject to the rights and limitations specified in the license contained in the applicable contract. -
File Systems
File Systems Profs. Bracy and Van Renesse based on slides by Prof. Sirer Storing Information • Applications could store information in the process address space • Why is this a bad idea? – Size is limited to size of virtual address space – The data is lost when the application terminates • Even when computer doesn’t crash! – Multiple process might want to access the same data File Systems • 3 criteria for long-term information storage: 1. Able to store very large amount of information 2. Information must survive the processes using it 3. Provide concurrent access to multiple processes • Solution: – Store information on disks in units called files – Files are persistent, only owner can delete it – Files are managed by the OS File Systems: How the OS manages files! File Naming • Motivation: Files abstract information stored on disk – You do not need to remember block, sector, … – We have human readable names • How does it work? – Process creates a file, and gives it a name • Other processes can access the file by that name – Naming conventions are OS dependent • Usually names as long as 255 characters is allowed • Windows names not case sensitive, UNIX family is File Extensions • Name divided into 2 parts: Name+Extension • On UNIX, extensions are not enforced by OS – Some applications might insist upon them • Think: .c, .h, .o, .s, etc. for C compiler • Windows attaches meaning to extensions – Tries to associate applications to file extensions File Access • Sequential access – read all bytes/records from the beginning – particularly convenient for magnetic tape • Random access – bytes/records read in any order – essential for database systems File Attributes • File-specific info maintained by the OS – File size, modification date, creation time, etc. -
Linux Cdrom Documentation
Linux Cdrom Documentation The kernel development community Jul 14, 2020 CONTENTS i ii CHAPTER ONE A LINUX CD-ROM STANDARD Author David van Leeuwen <[email protected]> Date 12 March 1999 Updated by Erik Andersen ([email protected]) Updated by Jens Axboe ([email protected]) 1.1 Introduction Linux is probably the Unix-like operating system that supports the widest variety of hardware devices. The reasons for this are presumably • The large list of hardware devices available for the many platforms that Linux now supports (i.e., i386-PCs, Sparc Suns, etc.) • The open design of the operating system, such that anybody can write a driver for Linux. • There is plenty of source code around as examples of how to write a driver. The openness of Linux, and the many different types of available hardware has al- lowed Linux to support many different hardware devices. Unfortunately, the very openness that has allowed Linux to support all these different devices has also allowed the behavior of each device driver to differ significantly from one device to another. This divergence of behavior has been very significant for CD-ROM devices; the way a particular drive reacts to a standard ioctl() call varies greatly from one device driver to another. To avoid making their drivers totally inconsis- tent, the writers of Linux CD-ROM drivers generally created new device drivers by understanding, copying, and then changing an existing one. Unfortunately, this practice did not maintain uniform behavior across all the Linux CD-ROM drivers. This document describes an effort to establish Uniform behavior across all the dif- ferent CD-ROM device drivers for Linux.