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Jonathan Wheeler E-Science Centre, RAL Introduction to XFS HEPSYSMAN 5 th December 2005.

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Presentation on theme: "Jonathan Wheeler E-Science Centre, RAL Introduction to XFS HEPSYSMAN 5 th December 2005."— Presentation transcript:

1 Jonathan Wheeler E-Science Centre, RAL Introduction to XFS HEPSYSMAN 5 th December 2005

2 Jonathan Wheeler e-Science Centre, RAL What exactly is a filesystem ? Organization: Large disk space to store small data items Use files and directories In UNIX everything is a stream of bytes: More complex file definition in other OSs Devices are also presented in the filesystem Linux uses virtual filesystems, e.g. /proc

3 Jonathan Wheeler e-Science Centre, RAL A little bit of background Three generation of UNIX filesystems: a)v7 / sysv / coherent / minix b)ffs / ext2 c)vxfs / ext3 / jfs / xfs / reiserfs

4 Jonathan Wheeler e-Science Centre, RAL Features of 3rd generation UNIX filesystems a)Intent logging / journaling b)Flexible metadata structures c)Dynamic inode allocations d)Extents

5 Jonathan Wheeler e-Science Centre, RAL History of XFS Developed by Silicon Graphics (now SGI) for use on IRIX: 1993 - original design 1994 - available for IRIX v 5.3 2000 - released as Open Source 2001/2002 – some Linux distributions with native XFS support 2003 – XFS support in 2.4 kernel

6 Jonathan Wheeler e-Science Centre, RAL XFS features (1) Journaling: but only metadata updates, not data updates. Fast Transactions: uses efficient B+ tree structures for fast searches and rapid space allocation

7 Jonathan Wheeler e-Science Centre, RAL XFS Features (2) 64-bit file system: a)64bit variables for global counters and disk addresses b)Large theoretical maximum filesystem size i.For Linux 2.4: 2 Terabytes. ii.For Linux 2.6 (when using 64 bit addressing on a 64 bit platform): 9 Petabytes (or the device limits) iii.For Linux 2.6 (on 32 bit platforms): 16Terabytes (even with 64 bit addressing) c)Maximum file size is same as filesystem size

8 Jonathan Wheeler e-Science Centre, RAL XFS Features (3) Partitioned into Allocation Groups: a)each AG manages its own free space and inodes b)provides scalability and parallelism within the file system c)limits the size of the structures needed to track this information

9 Jonathan Wheeler e-Science Centre, RAL XFS Features (3, continued) d)allows many internal pointers to be 32- bits e)AGs typically range in size from 0.5 to 4GB f)files and directories are not limited to a single AG.

10 Jonathan Wheeler e-Science Centre, RAL XFS Features (4) Sophisticated support utilities: a)fast mkfs (make a file system) b)dump and restore utilities for backup c)xfsrepair to fix corrupt filesystem d)xfs_fsr (XFS defragmenter) e)xfsdb (XFS debug) f)xfscheck (XFS check) g)xfs_growfs (enlarges filesystems online)

11 Jonathan Wheeler e-Science Centre, RAL Why you might want to use XFS a)Stable, mature code base (oldest journaling filesystem available on Unix) b)Very good performance for large reads or writes c)Designed for large systems d)Supports user and group quotas e)Support for Access Control Lists and Extended Attributes

12 Jonathan Wheeler e-Science Centre, RAL Extended Attributes An extended attribute is a name/value pair associated with a file. Attributes can be attached to all types of inodes: regular files, directories, symbolic links, device nodes, and so forth. Attribute values can contain up to 64KB of arbitrary binary data. See man attr for more details

13 Jonathan Wheeler e-Science Centre, RAL Extended attribute namespaces XFS implements three attribute namespaces: a)user namespace available to all users, protected by the normal file permissions b)system namespace, accessible only to privileged users and used for protected filesystem meta-data such as access control lists (ACLs) and hierarchical storage manager (HSM) file migration status c)security namespace used by security modules (SELinux)

14 Jonathan Wheeler e-Science Centre, RAL Why you might not want to use XFS a)No data journaling b)tar, cpio do not understand Extended Attributes

15 Jonathan Wheeler e-Science Centre, RAL Resources XFS/Linux homepage: http://oss.sgi.com/projects/xfs/ contains pointers to whitepapers, books, articles, etc. http://oss.sgi.com/projects/xfs/ Public mailing list: linux-xfs@oss.sgi.com with searchable list archivelinux-xfs@oss.sgi.com SGI Bugzilla database to report any bugs in XFS for Linux

16 Jonathan Wheeler e-Science Centre, RAL Comparison tests - 1 Tests were performed: on the same filesystem on the same hardware (AMD Athlon 1666 Mhz, 500Mb) using 3 different operating systems: i.Redhat 7.3 (2.4.20-28.7) ii.Scientific Linux version 3 (2.4.21-20.EL) iii.Scientific Linux version 4 (2.6.9-22.0.1.EL and 2.6.9.-11.EL.XFS)

17 Jonathan Wheeler e-Science Centre, RAL Comparison tests- 2 Tests used different filesystem types: RH 7.3 – ext2, ext3 (xfs not available) SL 3 – ext2, ext3 (attempts to create xfs filesystem caused system crash requiring hardware reset) SL 4 – ext2, ext3, xfs (default), xfs (custom: mkfs.xfs –d agsize=4g –i version=1 –I size=512 )

18 Jonathan Wheeler e-Science Centre, RAL Comparison tests - 3 Tests were performed: using bonnie++ test program (see http://www.coker.com.au/bonnie++) http://www.coker.com.au/bonnie using the same parameters for each test: /usr/local/sbin/bonnie++ -d /data \ -s 4096M:1024k \ -n 192:1048576:128:1024 -m csfnfs30 \ -u root 1>> outputfile 2>&1

19 Jonathan Wheeler e-Science Centre, RAL Comparison tests - 4 12 tests in total, each reporting filesystem performance and CPU use The first 6 tests measure I/O intensive work: Sequential output for character, blocked and rewrites Sequential input for character and blocked Random seeks

20 Jonathan Wheeler e-Science Centre, RAL Comparison tests - 6 The other 6 tests measure performance for many small files using: Sequential create, read and delete Random create, read and delete

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