Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
ATOL: Filesystems and Their Management
Marek Grác
xgrac@fi.muni.cz
Red Hat Czech s.r.o. / Faculty of Informatics, Masaryk University
Advanced Topics of Linux Administration
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Creating partiotions
fdisk (< 1.5 TB), cfdisk, parted ­ view and manage partition
tables
List partition tables from command line
partprobe ­ inform the OS of partition table changes
cat /proc/partitions
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Making Filesystems
mkfs
mkfs.ext2, mkfs.ext3, mkfs.msdos
Specific filesystem utilities can be called directly
mke2fs [options] device
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Filesystem Labels
Alternate way to refer to devices
Device independent
e2label devfile [fslabel]
mount [options] LABEL=fslabel mountpoint
blkid ­ used to see labels and filesystems type of all devices
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Mount Points and /etc/fstab
Configuration of the filesystem hierarchy
Used by mount, fsck and other programs
Maintains the hierarchy between system reboots
May use filesystem volume labels in the device field
The mount -a command cen be used to mount all filesystems
listed in /etc/fstab
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Unmounting Filesystems
umount [options] device|mountpoint
You cannot unmount a filesystem that is in use
Use fuser to check and/or kill processes
Use the remount option to change a mounted filesystem's
options atomically
mount -o remount,ro /data
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Handling Swap Files and Partitions
Swap space is a suppplement to system RAM
Basic setup involves:
Create a swap partition or file
Write special signature using mkswap
Add appropriate entries to /etc/fstab
Activate swap space with swapon -a
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Filesystems in Linux
Local disk file systems
ext2, ext3, ext4
reiserFS
XFS
Shared disk file systems (SAN vs NAS, cluster)
GFS, GFS2
GPFS
Lustre
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Extended file system (ext2, ext3)
Designed for Linux
ext2
Very stable
Through faultcan hurt filesystem
Repair is easy but quite slow
Inode size <= 128 for Windows driver
ext3 = ext2 + journaling
Backwards compatibility with ext2
Repair is fast (?) but some metadata operations are slow
Immutable files and append-only files
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
ReiserFS
ReiserFS3 in vanilla Linux kernel. Reiser4 not ready for
enterprise.
Reiser3
Good for small files
Not so stable
Less users, less support
Reiser4
Plugin driven filesystems
Transactions
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
XFS
One of the first journaling fs under UNIX (kernel 2.4.X)
Good for large files, big directories, big filesystems
Slow and problematic repair
Creation/Deletion of directory entries are slow
Quota can be set on per directory base
Features in XFS
Delayed allocation for reducing fragmentation
Native backup/restore utilities able to make fs dump without
unmounting
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
GFS
GFS2 is available in vanilla kernel since 2.6.19
Cluster filesystem
All nodes are equal, running are controlling access to shared
resources
Failure cluster member affects only other members using
shared resources
Features in GFS2:
Direct I/O support allows databases to achieve high
performance
Dynamic multi-path routing around failed components in SAN
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
GPFS
Proprietary, generally bundled with IBM hardware
Used on very large clusters (up to 2000 nodes)
High performance and grids
Features in GPFS:
SQL based syntax policies for file placement and management
Shared disk or network block IO configuration
Offer clustered NFS (HA)
Snapshot by copy-on-write
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Lustre
Not part of vanilla kernel, only patches
Architecture:
Uses modified ext3 as storage fs
Single metadata target
typicaly 2-8 object storage servers
clients accessing data
Features in Lustre:
Support for HA, recovery, transparent reboots
Data blocks stripped across objects (bandwidth agregation,
not limited by size of target object)
Slide by Pavol Babinčák
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Software RAID Configuration
Create and define RAID devices using mdadm
mdadm -C /dev/md0 -a yes -l 1 -n 2 -x 1 elements
Format each RAID device with a filesystem
mke2fs -k /dev/md0
Test the RAID devices
allows to check the status of your RAID devices
mdadm ­detail /dev/md0
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Software RAID Testing and Recovery
Simulating disk failures
mdadm /dev/md0 -f /dev/sda1
Recovering from a software RAID disk failure
replace the failed hard drive and power on
reconstruct partitions on the replacement drive
mdadm /dev/md0 -a /dev/sda1
mdadm, /proc/mdstat and syslog messages
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
What is Logical Volume Manager?
A layer of abstraction that allows easy manipulation of
volumes. Including resizing of filesystems.
Allow reorganization of filesystems across multiple physical
devices
Devices are designated as Physical Volumes (PV)
One or more PV are used to create a Volume Group (VG)
PV are defined with Physical Extents of a fixed size
Logical Volumes (LV) are created on PV and are composed of
Physical Extents
Filesystems may be created on Logical Volumes
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Creating Logical Volumes
Create physical volumes
pvcreate /dev/sda3
Assign physical volumes to volume groups
vgcreate vg0 /dev/sda3
Create logical volumes from volume groups
lvcreate -L 256M -n data vg0
mke2fs -j /dev/vg0/data
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Resizing Logical Volumes
Growing Volumes
lvextend can grow logical volumes
resize2fs can grow EXT3 filesystems online
vgextend adds new physical volumes to an existing volume
group
Shrinking Volumes
Filesystem have to be reduced first
Requires a filesystem check and cannot be performed online
lvreduce can then reduce volume
Volume Groups can be reduced with:
pvmove /dev/sda3
vgreduce vg0 /dev/sda3
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Lab: Installation
Goals:
Deploy LVM on the software RAID device
Create a group with two partitions such that new partition
could be added, and the filesystem could be extended
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management
Filesystems Management
RAID Devices
Logical Volumes Manager
Lab
Lab: Prepare a paper
Themes:
Compare software and hardware RAID
Compare new filesystems in Linux (ext4, zfs, reiser4, . . . )
Format:
Short presentation (15­20 minutes; 5-7 slides)
Paper containing comparision (1000 words)
Marek Grác xgrac@fi.muni.cz ATOL: Filesystems and Their Management