DOCSLIB.ORG

File System Metadata Virtualization by Ernest Artiaga I Amouroux

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
File System Metadata Virtualization by Ernest Artiaga I Amouroux UNIVERSITAT POLITÈCNICA DE CATALUNYA DEPARTMENT OF COMPUTER ARCHITECTURE File System Metadata Virtualization by Ernest Artiaga i Amouroux Advisor: Toni Cortés Rosselló A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor per la Universitat Politècnica de Catalunya File System Metadata Virtualization Abstract: The advance of computing systems has brought new ways to use and access the stored data that push the architecture of traditional file systems to its limits, making them inadequate to handle the new needs. Current challenges affect both the performance of high-end computing systems and the usability of general-purpose personal computing systems. One of the elements that limit the usability of file systems is the exposure of their internal organization through rigid name spaces, that usually reflect how data is actually stored in the underlying media. Users must know and understand the nuts and bolts of specific storage systems in order to achieve good results, receiving the burden of taking into account the complexities and restrictions of the new environments. This burden can be alleviated by providing dynamic, flexible name spaces adapted to specific application needs, instead of representing how data is stored in the underlying storage systems. This thesis contributes to the goal above by proposing a mechanism to decouple the user view of the storage from its underlying structure. This mechanism consists in the virtualization of file system metadata and the intro- duction of a sensible layer able to take automatic decisions on where and how the files should be stored in order to take advantage of the underlying storage system features. More specifically, the first contribution of this thesis is the design of a metadata virtualization framework which is able to produce consistent and flexible views of a file system, independently from the actual underlying data organization. The second contribution consists in using this framework to alleviate the complex file system tuning requirements in high-performance environments. Finally, The third contribution of this thesis consists in applying the metadata virtualization principles to provide an ubiquity layer for cloud storage systems that extends the cloud-awareness to the whole file system, making it independent from the directory where the cloud-related files reside. Keywords: File system virtualization, file system metadata, parallel file systems, cloud storage, name spaces. Place and date: Barcelona. October, 2013 Funding: This work was partially supported by Spanish MECD under grants TIN2007-60625 and TIN2012-34557, and the Catalan Government under the 2009-SGR-980 grant. Part of the research leading to the presented results has also received funding from the EU IST program as part of the XtreemOS project (contract FP6-033576) and the European Community’s Seventh Frame- work Programme (FP7/2007-2013) under grant agreement RI-283493, as part of the PRACE-2IP project. Infrastructure: Part of the research in this thesis has been possible thanks to the high- performance computing infrastructures kindly provided by the Barcelona Supercomputing Center (BSC), the Partnership for Advanced Computing in Europe (PRACE) and the Lawrence-Livermore National Laboratory (LLNL) via the Hyperion Project; additionally, part of the works in this thesis have made use of the computing infrastructure of the Department of Computer Architecture at the Technical University of Catalonia (DAC-UPC). I sincerely acknowledge their support. Acknowledgements This thesis is part of a long path that started many years ago, and I have met many people that have supported me along the way and helped me in critical moments. All of them have contributed in some way to this work, I sincerely acknowledge their part in the effort. Specially, I would like to thank Mateo Valero for giving me the opportunity of working at BSC since its beginning and dedicating these last years to research. Thanks to that, I have had access to both the people and the technological resources that have enabled me to pursue my PhD. I would not be finishing my thesis now without his support. All journeys have a start, and I would not have reached this point without the continuous support of Pep Fuertes. He was the person that many years ago started to push me into the world of research, and trusted me even before I finished my Computer Science courses at University. I have learned many valuable things from him, and I owe many of my achievements to his advice, encouragement and friendship during all these years. The day to day efforts leading to my PhD have been assisted by Toni Cortés who, despite knowing me, accepted to be my advisor. His vision and wisdom have indeed contributed to the happy ending of my PhD, and his friendliness and optimism have created a wonderful and interesting place to work. I want to thank the current and former members of the Storage Systems Research Group at BSC for being a wonderful team to work in. I have received many useful inputs from them. In particular, Jonathan Martí, Jan Wiberg, Juan González de Benito and Thanos Makatos have had an important participation in the technical aspects related to this thesis. I must specially mention Alberto Miranda, whose abilities and curiosity make of him an amazing source of information and technical knowledge, apart from a nice colleague to work with. The use of the supercomputing infrastructures required for the present work has been greatly facilitated by the Operations team at BSC. I really appreciate the help from the system administrators and the support team to prepare the rather uncon- ventional setups required for my experiments. I specially want to thank to Javier Bartolomé, David Vicente, Sergi Moré, Jordi Valls and Albert Benet their readiness to collaborate, and the help of Ferran Sellés, Toni Espinar, Pedro Gómez and Albert Riera to solve any issues in the working environment. I want to mention the people from the Operating Systems Group at the Depart- ment of Computer Architecture who shared my first steps (and specially Xavier Martorell, whom I honestly admire for his ability to comprehend all aspects of a system at any arbitrary level of detail). Since then, a lot of people from the Depart- ment of Computer Architecture at UPC and from the BSC have made my life easier by sharing their knowledge, but also breakfasts, coffees, meals and discussions about spherical cows. I am afraid that the list is too long to mention you all, but I really appreciate your company. I specially want to thank David Carrera, Marc González vi and Anna Queralt for consistently being able to cast away any worries during lunch times. I have a very long list of reasons to say thanks to Yolanda Becerra, and excellent colleague and good friend since school time. She has that rare quality of being reliable on good and bad times, and so many times she has helped me to stay focused during trouble. Thanks for always being there! I also want to thank my friends for helping me to have a life outside the work. Specially Pedro, Oriol, Maria José, Rosa, Sandra and Nacho who, even when life makes it difficult to meet often, continue being great friends. And I cannot forget my family for being by my side at all times. Specially my uncles, my cousins (Edu, Anna and Núria) and my new family in Granada (Manolo and Ana). Above all, I want to thank my mother, Pilar, for always being caring and teaching me everything I needed to prepare for life, and to my grandmother, Carmen, who would have enjoyed seeing this work finished. Finally, I want to thank Pili, my wife, for her sustained support during all these years, for her patience and for making my life a happier place. Her energy has always inspired me to go on. Thanks for sharing your life with me! Agraïments Aquesta tesi és part d’un llarg camí que va començar fa molts anys, durant el qual he trobat a molta gent que m’ha anat ajudant, especialment en els moments crítics. Tots ells han aportat d’alguna forma el seu gra de sorra a aquest treball i desitjo agraïr-los sincerament la seva contribució. En particular, m’agradaria agrair a Mateo Valero que em donés l’oportunitat de treballar al BSC des de la seva creació i poder dedicar aquests últims anys a la recerca. Gràcies a això he pogut tenir accés tant a la gent com als recursos tecnològics que m’han permès fer el doctorat. Sense el seu suport, no estaria ara escrivint aquestes línies. Tots els camins tenen un començament, i no hauria arribat a aquest moment sense el suport continu d’en Pep Fuertes. Ell va ser la persona que, fa molts anys, em va introduir en el món de la recerca, confiant en mi fins i tot abans que acabés la carrera d’Informàtica. He tingut la sort de poder aprendre moltes coses d’ell, i moltes de les coses que he aconseguit fer les dec al seus consells, el seu suport i la seva amistat durant tots aquests anys. Els esforços del dia a dia que han portat a la conclusió del meu doctorat han estat guiats per en Toni Cortés qui, tot i que em coneixia, va acceptar dirigir-me la tesi. La seva visió de la tecnologia i la seva experiència han contribuït de forma decisiva a que el meu doctorat tingués un bon final; la seva amistat i el seu optimisme han creat un espai interessant per treballar-hi. Vull agrair als membres i ex-membres del Storage Systems Research Group del BSC per haver format un equip fantàstic. D’ells he rebut moltes aportacions. En particular, en Jonathan Martí, en Jan Wiberg, en Juan González de Benito i en Thanos Makatos han tingut una participació destacada en els aspectes tècnics relacionats amb aquesta tesi.
Load more

Recommended publications
  • 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.
    [Show full text]
  • Enhancing the Accuracy of Synthetic File System Benchmarks Salam Farhat Nova Southeastern University, [email protected]
    Nova Southeastern University NSUWorks CEC Theses and Dissertations College of Engineering and Computing 2017 Enhancing the Accuracy of Synthetic File System Benchmarks Salam Farhat Nova Southeastern University, [email protected] This document is a product of extensive research conducted at the Nova Southeastern University College of Engineering and Computing. For more information on research and degree programs at the NSU College of Engineering and Computing, please click here. Follow this and additional works at: https://nsuworks.nova.edu/gscis_etd Part of the Computer Sciences Commons Share Feedback About This Item NSUWorks Citation Salam Farhat. 2017. Enhancing the Accuracy of Synthetic File System Benchmarks. Doctoral dissertation. Nova Southeastern University. Retrieved from NSUWorks, College of Engineering and Computing. (1003) https://nsuworks.nova.edu/gscis_etd/1003. This Dissertation is brought to you by the College of Engineering and Computing at NSUWorks. It has been accepted for inclusion in CEC Theses and Dissertations by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Enhancing the Accuracy of Synthetic File System Benchmarks by Salam Farhat A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor in Philosophy in Computer Science College of Engineering and Computing Nova Southeastern University 2017 We hereby certify that this dissertation, submitted by Salam Farhat, conforms to acceptable standards and is fully adequate in scope and quality to fulfill the dissertation requirements for the degree of Doctor of Philosophy. _____________________________________________ ________________ Gregory E. Simco, Ph.D. Date Chairperson of Dissertation Committee _____________________________________________ ________________ Sumitra Mukherjee, Ph.D. Date Dissertation Committee Member _____________________________________________ ________________ Francisco J.
    [Show full text]
  • CS 5600 Computer Systems
    CS 5600 Computer Systems Lecture 10: File Systems What are We Doing Today? • Last week we talked extensively about hard drives and SSDs – How they work – Performance characterisEcs • This week is all about managing storage – Disks/SSDs offer a blank slate of empty blocks – How do we store files on these devices, and keep track of them? – How do we maintain high performance? – How do we maintain consistency in the face of random crashes? 2 • ParEEons and MounEng • Basics (FAT) • inodes and Blocks (ext) • Block Groups (ext2) • Journaling (ext3) • Extents and B-Trees (ext4) • Log-based File Systems 3 Building the Root File System • One of the first tasks of an OS during bootup is to build the root file system 1. Locate all bootable media – Internal and external hard disks – SSDs – Floppy disks, CDs, DVDs, USB scks 2. Locate all the parEEons on each media – Read MBR(s), extended parEEon tables, etc. 3. Mount one or more parEEons – Makes the file system(s) available for access 4 The Master Boot Record Address Size Descripon Hex Dec. (Bytes) Includes the starEng 0x000 0 Bootstrap code area 446 LBA and length of 0x1BE 446 ParEEon Entry #1 16 the parEEon 0x1CE 462 ParEEon Entry #2 16 0x1DE 478 ParEEon Entry #3 16 0x1EE 494 ParEEon Entry #4 16 0x1FE 510 Magic Number 2 Total: 512 ParEEon 1 ParEEon 2 ParEEon 3 ParEEon 4 MBR (ext3) (swap) (NTFS) (FAT32) Disk 1 ParEEon 1 MBR (NTFS) 5 Disk 2 Extended ParEEons • In some cases, you may want >4 parEEons • Modern OSes support extended parEEons Logical Logical ParEEon 1 ParEEon 2 Ext.
    [Show full text]
  • 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.
    [Show full text]
  • W4118: Linux File Systems
    W4118: Linux file systems Instructor: Junfeng Yang References: Modern Operating Systems (3rd edition), Operating Systems Concepts (8th edition), previous W4118, and OS at MIT, Stanford, and UWisc File systems in Linux Linux Second Extended File System (Ext2) . What is the EXT2 on-disk layout? . What is the EXT2 directory structure? Linux Third Extended File System (Ext3) . What is the file system consistency problem? . How to solve the consistency problem using journaling? Virtual File System (VFS) . What is VFS? . What are the key data structures of Linux VFS? 1 Ext2 “Standard” Linux File System . Was the most commonly used before ext3 came out Uses FFS like layout . Each FS is composed of identical block groups . Allocation is designed to improve locality inodes contain pointers (32 bits) to blocks . Direct, Indirect, Double Indirect, Triple Indirect . Maximum file size: 4.1TB (4K Blocks) . Maximum file system size: 16TB (4K Blocks) On-disk structures defined in include/linux/ext2_fs.h 2 Ext2 Disk Layout Files in the same directory are stored in the same block group Files in different directories are spread among the block groups Picture from Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 3 Block Addressing in Ext2 Twelve “direct” blocks Data Data BlockData Inode Block Block BLKSIZE/4 Indirect Data Data Blocks BlockData Block Data (BLKSIZE/4)2 Indirect Block Data BlockData Blocks Block Double Block Indirect Indirect Blocks Data Data Data (BLKSIZE/4)3 BlockData Data Indirect Block BlockData Block Block Triple Double Blocks Block Indirect Indirect Data Indirect Data BlockData Blocks Block Block Picture from Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc.
    [Show full text]
  • Online Layered File System (OLFS): a Layered and Versioned Filesystem and Performance Analysis
    Loyola University Chicago Loyola eCommons Computer Science: Faculty Publications and Other Works Faculty Publications 5-2010 Online Layered File System (OLFS): A Layered and Versioned Filesystem and Performance Analysis Joseph P. Kaylor Konstantin Läufer Loyola University Chicago, [email protected] George K. Thiruvathukal Loyola University Chicago, [email protected] Follow this and additional works at: https://ecommons.luc.edu/cs_facpubs Part of the Computer Sciences Commons Recommended Citation Joe Kaylor, Konstantin Läufer, and George K. Thiruvathukal, Online Layered File System (OLFS): A layered and versioned filesystem and performance analysi, In Proceedings of Electro/Information Technology 2010 (EIT 2010). This Conference Proceeding is brought to you for free and open access by the Faculty Publications at Loyola eCommons. It has been accepted for inclusion in Computer Science: Faculty Publications and Other Works by an authorized administrator of Loyola eCommons. For more information, please contact [email protected]. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License. Copyright © 2010 Joseph P. Kaylor, Konstantin Läufer, and George K. Thiruvathukal 1 Online Layered File System (OLFS): A Layered and Versioned Filesystem and Performance Analysis Joe Kaylor, Konstantin Läufer, and George K. Thiruvathukal Loyola University Chicago Department of Computer Science Chicago, IL 60640 USA Abstract—We present a novel form of intra-volume directory implement user mode file system frameworks such as FUSE layering with hierarchical, inheritance-like namespace unifica- [16]. tion. While each layer of an OLFS volume constitutes a subvol- Namespace Unification: Unix supports the ability to ume that can be mounted separately in a fan-in configuration, the entire hierarchy is always accessible (online) and fully navigable mount external file systems from external resources or local through any mounted layer.
    [Show full text]
  • Ext3 = Ext2 + Journaling
    FS Sistem datoteka-skup metoda i struktura podataka koje operativni sistem koristi za čuvanje podataka Struktura sistema datoteka: - 1. zaglavlje→neophodni podaci za funkcionisanje sistema datoteka - 2. strukture za organizaciju podataka na medijumu→meta podaci - 3. podaci→datoteke i direktorijumi Strukture podataka neophodne za realizaciju sistema datoteka: - PCB(Partition Control Block) - BCB(Boot control Block) - Kontrolne strukture za alokaciju datoteka(i-node tabela kod Linux-a) - Direktorijumske strukture koje sadrže kontrolne blokove datoteka - FCB(File Control Block) ext3 Slide 1 of 51 VIRTUELNI SISTEM DATOTEKA(VFS) Linux podržava rad sa velikim brojem sistema datoteka(ext2,ext3, XFS,FAT, NTFS...) VFS-objektno orjentisani način realizacije sistema datoteka koji omogućava korisniku da na isti način pristupa svim sistemima datoteka Način obraćanja korisnika sistemu datoteka - korisnik->API - VFS->sistem datoteka ext3 Slide 2 of 51 Linux FS Linux posmatra svaki sistem datoteka kao nezavisnu hijerarhijsku strukturu objekata(datoteka i direktorijuma) na čijem se vrhu nalazi root(/) direktorijum Objekti Linux sistema datoteka: Super block - zaglavlje(superblock) - i-node tabela I-Node Table - blokovi sa podacima - direktorijumski blokovi - blokovi indirektnih pokazivača Data Area i-node-opisuje objekte, oko 128B na disku Kompromis između veličine i-node tabele i brzine rada sistema datoteka - prvih 10-12 pokazivača na blokove sa podacima - za alokaciju većih datoteka koristi se single indirection block - za još veće datoteke
    [Show full text]
  • Ivoyeur: Inotify
    COLUMNS iVoyeur inotify DAVE JOSEPHSEN Dave Josephsen is the he last time I changed jobs, the magnitude of the change didn’t really author of Building a sink in until the morning of my first day, when I took a different com- Monitoring Infrastructure bination of freeways to work. The difference was accentuated by the with Nagios (Prentice Hall T PTR, 2007) and is Senior fact that the new commute began the same as the old one, but on this morn- Systems Engineer at DBG, Inc., where he ing, at a particular interchange, I would zig where before I zagged. maintains a gaggle of geographically dispersed It was an unexpectedly emotional and profound metaphor for the change. My old place was server farms. He won LISA ‘04’s Best Paper off to the side, and down below, while my future was straight ahead, and literally under award for his co-authored work on spam construction. mitigation, and he donates his spare time to the SourceMage GNU Linux Project. The fact that it was under construction was poetic but not surprising. Most of the roads I [email protected] travel in the Dallas/Fort Worth area are under construction and have been for as long as anyone can remember. And I don’t mean a lane closed here or there. Our roads drift and wan- der like leaves in the water—here today and tomorrow over there. The exits and entrances, neither a part of this road or that, seem unable to anticipate the movements of their brethren, and are constantly forced to react.
    [Show full text]
  • 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.
    [Show full text]
  • Virtual File System (VFS) Implementation in Linux
    Virtual File System (VFS) Implementation in Linux Tushar B. Kute, http://tusharkute.com Virtual File System • The Linux kernel implements the concept of Virtual File System (VFS, originally Virtual Filesystem Switch), so that it is (to a large degree) possible to separate actual "low-level" filesystem code from the rest of the kernel. • This API was designed with things closely related to the ext2 filesystem in mind. For very different filesystems, like NFS, there are all kinds of problems. Virtual File System- Main Objects • The kernel keeps track of files using in-core inodes ("index nodes"), usually derived by the low-level filesystem from on-disk inodes. • A file may have several names, and there is a layer of dentries ("directory entries") that represent pathnames, speeding up the lookup operation. • Several processes may have the same file open for reading or writing, and file structures contain the required information such as the current file position. • Access to a filesystem starts by mounting it. This operation takes a filesystem type (like ext2, vfat, iso9660, nfs) and a device and produces the in-core superblock that contains the information required for operations on the filesystem; a third ingredient, the mount point, specifies what pathname refers to the root of the filesystem. Virtual File System The /proc filesystem • The /proc filesystem contains a illusionary filesystem. • It does not exist on a disk. Instead, the kernel creates it in memory. • It is used to provide information about the system (originally about processes, hence the name). • The proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures.
    [Show full text]
  • Measuring Parameters of the Ext4 File System
    File System Forensics : Measuring Parameters of the ext4 File System Madhu Ramanathan Venkatesh Karthik Srinivasan Department of Computer Sciences, UW Madison Department of Computer Sciences, UW Madison [email protected] [email protected] Abstract An extent is a group of physically contiguous blocks. Allocating Operating systems are rather complex software systems. The File extents instead of indirect blocks reduces the size of the block map, System component of Operating Systems is defined by a set of pa- thus, aiding the quick retrieval of logical disk block numbers and rameters that impact both the correct functioning as well as the per- also minimizes external fragmentation. An extent is represented in formance of the File System. In order to completely understand and an inode by 96 bits with 48 bits to represent the physical block modify the behavior of the File System, correct measurement of number and 15 bits to represent length. This allows one extent to have a length of 215 blocks. An inode can have at most 4 extents. those parameters and a thorough analysis of the results is manda- 15 tory. In this project, we measure the various key parameters and If the file is fragmented, every extent typically has less than 2 a few interesting properties of the Fourth Extended File System blocks. If the file needs more than four extents, either due to frag- (ext4). The ext4 has become the de facto File System of Linux ker- mentation or due to growth, an extent HTree rooted at the inode is nels 2.6.28 and above and has become the default file system of created.
    [Show full text]
  • Migrating from Netware to OES 2 Linux
    Best Practice Guide www.novell.com Migrating from NetWare to OES 2 prepared for Novell OES 2 User Community Published: November, 2007 Disclaimer Novell, Inc. makes no representations or warranties with respect to the contents or use of this document, and specifically disclaims any express or implied warranties of merchantability or fitness for any particular purpose. Trademarks Novell is a registered trademark of Novell, Inc. in the United States and other countries. * All third-party trademarks are property of their respective owner. Copyright 2007 Novell, Inc. All rights reserved. No part of this publication may be reproduced, photocopied, stored on a retrieval system, or transmitted without the express written consent of Novell, Inc. Novell, Inc. 404 Wyman Suite 500 Waltham Massachusetts 02451 USA Prepared By Novell Services and User Community Migrating from NetWare to OES 2—Best Practice Guide November, 2007 Novell OES 2 User Community The latest version of this document, along with other OES 2 Linux Best Practice Guides, can be found with the NetWare to Linux Migration Resources at: http://www.novell.com/products/openenterpriseserver/netwaretolinux/view/all/-9/tle/all Contents Acknowledgments.................................................................................. iv Getting Started...................................................................................... 1 Why OES 2?..............................................................................................1 Which Services Are Right for OES 2? ................................................................4
    [Show full text]