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O’Reilly Open Source Convention 2000
Linux Filesystems for Real-World Needs
Æleen Frischaefrisch@lorentzian.com
www.aeleen.com
exponential Consulting, LLCNorth Haven, Connecticut, USA
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
2
Itinerary
The Kernel’s VFS Local Filesystems Network Shared Filesystems Advanced Filesystems Futures
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
3
Virtual File System (VFS)
Kernel subsystem Provides a consistent interface for
low-level file I/O Filesystem needs only use that API and
provide specified functionality, andit is automatically supported.
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
4
Filesystems for Local Disks
Lots of supported types: ext2 CD-ROM: iso9660, Microsoft Joliet extensions ufs, fat, vfat, umsdos, ntfs, sysv, affs, adfs,
hfs, hpfs, qnx4, … minix procfs /dev/pts
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
5
Journaled Filesystems
ReiserFS in SuSE 6.3 ext3 dtfs:
www.complang.tuwien.ac.at/czezatke/lfs.html
SGI’s xfs being ported
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
6
Network Filesystems
NFS AFS smbfs ncpfs
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
7
Linux NFS
Longtime weak spot Unreliable Poor performance
nfsstones benchmark
Unable to communicate with non-Linux clients knfsd is what you want to use
Need to upgrade all current distributions as delivered to latest available version Kernel patches New daemon New utilities
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
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Production Filesystem Features
Bigger than one disk partition (flexibility) Faster I/O Fault tolerant Distributed
Load balancing
Enhanced Security Access Control Lists Encryption
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
9
Logical Volumes
Dynamically-resizable filesystem consisting of multiple, independent disk partitions (physical volumes), upon which a virtual structure is imposed: Volume groups--virtual disks-- divisible into … Logical volume--virtual partitions--which hold … Filesystems
Common in modern OS’s: AIX, HP, True64
Logical Volume Manager (lvm): alpha code Veritas Volume Manager: $$$$
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
forReal-World
Needs
10
lvm
linux.msede.com/lvm/ Basics seem to work, but still Alpha code
(version 0.7) Maximum (theoretical) filesystem size:
> 1000 TB
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
11
lvm Commands
pv: create, change, display vg: create, change, display, ck,
cfgbackup/restore, export, extend, reduce, remove, split
lv: create, change, display, extend, reduce, remove e2fsadm (needs PartitionMagic’s resize2fs)
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
forReal-World
Needs
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lvm Example
Run fdisk to set partition type to 0xFE pvcreate /dev/sdb1 /dev/sdc1 vgcreate new_vg /dev/sd{b,c}1
/dev/new_vg/group /etc/lvmconf/new_vg.conf
lvcreate –L 2g –n new_lv –r 4 –C y mke2fs /dev/new_vg/new_lv mount /dev/new_vg/new_lv /somewhere
e2fsadm –L +500m /dev/new_vg/new_lv vs. lvextend
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
13
RAID
Redundant Arrays of Inexpensive Disks
Choices Software Hardware
Controller RAID device
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
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Needs
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RAID Levels
0: Disk striping—performance onlyBest large transfer I/O bandwidthNo loss of storage capacity
1: Disk mirroringBest data redundancyGood performance on small transfers
3: Disk striping with parity diskOptimizes I/O bandwidth for large transfers Low impact of single disk failure
Obsolete!
5: Parity block rotates among component disksOptimizes I/O operations/secNot vulnerable to single disk failure
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
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Linux RAID
0, 1, 4(!), 5 Linear
Kernel support must be enabled Patches needed (still):
ftp.*.kernel.org/pub/linux/daemons/raid/alpha RedHat installs for you
Special files: /dev/mdx Configuration file: /etc/raidtab
mkraid [device] Persistent superblock
Automatic detection raidstart and raidstop to control manually
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
16
Kernel Support
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
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Sample /etc/raidtab Entries
Raid 0: Striping
raiddev /dev/md0raid-level 0nr-raid-disks 2chunk-size 64
persistent-superblock 1device /dev/sdc1
raid-disk 0device /dev/sdd1
raid-disk 1
Raid 1: Mirroring
raiddev /dev/md0raid-level 1nr-raid-disks 2
persistent-superblock 1device /dev/sdc1
raid-disk 0device /dev/sdd1
raid-disk 1
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
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Needs
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Mirroring a Striped Disk: “RAID 10”
raiddev /dev/md0raid-level 0nr-raid-disks 2chunk-size 64k
…device /dev/sdc1
raid-disk 0device /dev/sdd1
raid-disk 1
raiddev /dev/md1raid-level 0nr-raid-disks 2chunk-size 64k
device /dev/sde1raid-disk 0
device /dev/sdf1raid-disk 1
raiddev /dev/md2raid-level 1nr-raid-disks 2
device /dev/md0raid-disk 0
device /dev/md1raid-disk 1
But why?
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
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Needs
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RAID 5
raiddev /dev/md0raid-level 5nr-raid-disks 3nr-spare-disks 1persistent-superblock 1
device /dev/sdc1raid-disk 0
device /dev/sdd1raid-disk 1
device /dev/sde1raid-disk 2
device /dev/sdf1spare-disk 0
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
forReal-World
Needs
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General RAID Considerations
Stripe size matters! Best value depends on typical I/O transfer size Testing: trial and error
Underlying filesystem block size = 4K mke2fs –b 4 …
Don’t overload controllers
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
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Coda
Follow-on to the Andrew File System (AFS) www.coda.cs.cmu.edu
Distributed filesystem: /coda on client can have components (“volumes”)
from all over the network (transparent to user)
Lots of metadata, stored in a database, using logging and other transaction-based procedure to ensure integrity
Complex configuration task
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
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Needs
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Coda Features
Read-write data replication Automatic modification propogation and
synchronization/repair
Caching (performance, network failures, mobile computing) Client-requested files
Automatic update requests Client-modifications when server is unavailable; attempts
automatic synchronization of conflicts
Kerberos-like authentication tokens Access control lists
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
23
Intermezzo
www.inter-mezzo.com Distributed file system
Designed for high availability Palimpsest on Coda
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
forReal-World
Needs
24
Global File System (GFS)
www.globalfilesystem.org Network-shared storage
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
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Needs
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Access Control Lists
POSIX ACLs Alpha code
Recent call for testing …
Specifies file access on per-user/group basis ACLs inherited from parent directory Deny>Allow (null=>deny)
Copyright © 1999-2000,Exponential Consulting,
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LinuxFilesystems
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Enabling ACLs
Patch and build kernel Prompt for development option
Get/build utilities Patch and build ext2fs utilities
mount … -o acl setfacl and getfact Do frequent backups (files and ACLs)
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
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Needs
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Encryption
Encryption Steganography
Filesystem hidden in the low bits of each byte of an audio file
EFS ftp.csua.berkeley.edu/pub/cypherpunks/
filesystems/linux
PPDD linux01.gwdg.de/~alatham/ppdd.html
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
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Setup
Patch/configure/build kernel Get/build utilities Patch/rebuild standard tools
dd to create file losetup to set algorithm and pass phrase mke2fs
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
29
Using an Encrypted filesystem
fstab: device mount-pt ext2 defaults,noauto,loop,encryption=type 0 0
Prompted for pass phrase when filesystem is mounted
Copyright © 1999-2000,Exponential Consulting,
LLC
LinuxFilesystems
forReal-World
Needs
30
Filesystem Futures
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