Red Hat - LVM - Mazenet Solution
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The document provides an overview of Logical Volume Management (LVM) in Linux, detailing its purpose, advantages, and basic operations for managing storage configurations. It explains the layers of storage from disks to filesystems and introduces essential commands for creating, modifying, and removing physical and logical volumes. The document emphasizes circumstances under which LVM should or should not be used, and offers a guide to its functionalities and best practices.
![Commands used in LVM
adding
pvcreate /dev/sdb1
## Create physical volume with specific UUID, used to recover volume groups (see
miscellaneous section)
pvcreate --uuid <UUID> /dev/sdb1
removing pvremove /dev/sdb1
moving
pvmove -v /dev/sdb2 /dev/sdb3
Note: moves any used extents from this volume to another volume, in readiness to remove that
volume. However you cannot use this on mirrored volumes, you must convert back to non-
mirror using "lvconvert -m 0"
Volume Groups
creating
vgcreate VolData00 /dev/sdb1 /dev/sdb2 /dev/sdb3
vgcreate VolData00 /dev/sdb[123]
vgcreate VolData00 -s 32 /dev/sdb1
Common Attributes that you may want to use:
-l maximum logical volumes
-p maximum physical volumes
-s physical extent size (default is 4MB)
-A autobackup](https://image.slidesharecdn.com/lvm-160614090917/85/Red-Hat-LVM-Mazenet-Solution-14-320.jpg)
![Commands used in LVM
extending vgextend VolData00 /dev/sdb3
reducing
vgreduce VolData00 /dev/sdb3
vgreduce --removemissing --force VolData00
removing
vgremove VolData00
Common Attributes that you may want to use:
-f force the removal of any logical volumes
merging
# the old volumes group will be merged into the new volume group
vgmerge New_Vol_Group Old_Vol_Group
Note: you must unmount any fielsystems and deactivate the vg that is being
merged "vgchange -a n <vg>", then you can activiate it again afterwards
"vgchange -a y <vg>", then perform a vgscan, dont forget to backup the
configuration
spliting
vgsplit Old_Vol_Group New_Vol_Group [physical volumes] [-n logical
volume name]](https://image.slidesharecdn.com/lvm-160614090917/85/Red-Hat-LVM-Mazenet-Solution-15-320.jpg)
![extending
lvextend -L 20M /dev/VolData00/vol01
Note: you can extend a ext2/ext3 filesystem using the "resize2fs" or "fsadm"
command
fsadm resize /dev/VolData01/data01
resize2fs -p /dev/mapper/VolData01-data01 [size]
The -p option displays bars of progress while extendingthe filesystem
reducing/resizing
lvreduce -L 5M /dev/VolData00/vol01
lvresize -L 5M /dev/VolData00/vol01
Note: rounding will occur when extending and reducing volumes to the next extent
(4MB by default), you can use resize2fs or fsadm to shrink the filesystem
fsadm resize /dev/VolData01/data01 [size]
resize2fs -p /dev/mapper/VolData01-data01 [size]
removing lvremove /dev/VolData00/vol01](https://image.slidesharecdn.com/lvm-160614090917/85/Red-Hat-LVM-Mazenet-Solution-17-320.jpg)
Red Hat - LVM - Mazenet Solution
- 1. LVM VIMAL THAMIZHARASAN SENIOR LINUX TRAINER MAZENET SOLUTION-CHENNAI,T-NAGAR.
- 2. Agenda • Some basic background about Files and Filesystems under Linux • What is LVM and why should I use it • How to create a simple LVM environment
- 3. What is Logical Volume Management? • Software that allows the user to edit the storage configuration without • manipulating the actual hardware and vice versa.
- 4. When to and not use LVMs • USE WHEN: -Lots of DISKs and you need to simplify -Need flexiblity of file system expansion -When you want to learn an advanced storage management topic • DON'T USE: -SINGLE Partition Environments -If Command line (CLI) is scary to you -Without access to a System Administrator :
- 5. How Does LVM Work? The LVM hides information about where information is stored, on which hardware, and where exactly on that hardware from the entire Operating System allowing it to manipulate the configuration of the storage capacities.
- 6. Layers to make it easier • Layers in a typical system (before LVM) Files/Dirs Filesystems Partitions Disks
- 7. What is a Disk? • The harddisk is the only Hardware piece we're going to talk about here • It has various techie things in it: - Cylinders, Heads, Sectors, mbr, partitions - It's own cpu, cache, firmware etc. • but for this discussion a hard disk on a modern system can be seen as one continuous row of logical blocks. • Typical disk names in Linux are hda, sda,vda.
- 8. Partitions • To store data on a disk this continuous row of logical blocks needs to be cut in sections called Partitions. • The original IBM PC from 1981 only had 4 primary partitions. • This was later improved by adding extended partitions • Normally managed by fdisk or some graphical partition/volume manager. • One partition must be a continuous chunk of blocks .
- 9. Filesystems • Filesystems are a fancy way to hold together a group of files and directories. • Without LVM one filesystem=one partition. • Common File Systems: -In the Windows World: FAT (dos) FAT12/16/32 NTFS -In Linux Ext2/3, Reiserfs,jfs,xfs And many many more
- 10. Files on a linux (and unix) system • At last we are at the top, the user level • Within User Level we have –Files –Directories –Filesystems Files Hold Data • Directories hold files and directories • Filesystems holds directories and files • Mount points hold Filesystems
- 12. • By adding another layer between partitions and filesystems we break the OneFS=OnePartition relation • This have many advantages • 2 special reasons: –Can carve out non continues filesystems –Can add disks partitions together so they look like one big disk
- 13. Commands used in LVM Directory and Files Directories and Files ## Directories /etc/lvm - default lvm directory location /etc/lvm/backup - where the automatic backups go /etc/lvm/cache - persistent filter cache /etc/lvm/archive - where automatic archives go after a volume group change /var/lock/lvm - lock files to prevent metadata corruption # Files /etc/lvm/lvm.conf - main lvm configuration file $HOME/.lvm - lvm history Physical Volumes display pvdisplay -v pvs -v pvs -a
- 14. Commands used in LVM adding pvcreate /dev/sdb1 ## Create physical volume with specific UUID, used to recover volume groups (see miscellaneous section) pvcreate --uuid <UUID> /dev/sdb1 removing pvremove /dev/sdb1 moving pvmove -v /dev/sdb2 /dev/sdb3 Note: moves any used extents from this volume to another volume, in readiness to remove that volume. However you cannot use this on mirrored volumes, you must convert back to non- mirror using "lvconvert -m 0" Volume Groups creating vgcreate VolData00 /dev/sdb1 /dev/sdb2 /dev/sdb3 vgcreate VolData00 /dev/sdb[123] vgcreate VolData00 -s 32 /dev/sdb1 Common Attributes that you may want to use: -l maximum logical volumes -p maximum physical volumes -s physical extent size (default is 4MB) -A autobackup
- 15. Commands used in LVM extending vgextend VolData00 /dev/sdb3 reducing vgreduce VolData00 /dev/sdb3 vgreduce --removemissing --force VolData00 removing vgremove VolData00 Common Attributes that you may want to use: -f force the removal of any logical volumes merging # the old volumes group will be merged into the new volume group vgmerge New_Vol_Group Old_Vol_Group Note: you must unmount any fielsystems and deactivate the vg that is being merged "vgchange -a n <vg>", then you can activiate it again afterwards "vgchange -a y <vg>", then perform a vgscan, dont forget to backup the configuration spliting vgsplit Old_Vol_Group New_Vol_Group [physical volumes] [-n logical volume name]
- 16. Commands used in LVM Logical Volumes display lvdisplay -v lvdisplay --maps display mirror volumes lvs -v lvs -a -o +devices ## lvs commands for mirror volumes lvs -a -o +devices lvs -a -o +seg_pe_ranges --segments ## Stripe size lvs -v --segments lvs -a -o +stripes,stripesize scanning lvscan -v lvmdiskscan creating ## plain old volume lvcreate -L 10M VolData00 ## plain old volume but with a specific name web01 lvcreate -L 10M -n web01 VolData00 ## plain old volume but on a specific disk lvcreate -L 10M VolData00 /dev/sdb1 ## a striped volume called lvol1 (note the captial i for the stripe size), can use -l (extents) instead of -L lvcreate -i 3 -L 24M -n lvol1 vg01
- 17. extending lvextend -L 20M /dev/VolData00/vol01 Note: you can extend a ext2/ext3 filesystem using the "resize2fs" or "fsadm" command fsadm resize /dev/VolData01/data01 resize2fs -p /dev/mapper/VolData01-data01 [size] The -p option displays bars of progress while extendingthe filesystem reducing/resizing lvreduce -L 5M /dev/VolData00/vol01 lvresize -L 5M /dev/VolData00/vol01 Note: rounding will occur when extending and reducing volumes to the next extent (4MB by default), you can use resize2fs or fsadm to shrink the filesystem fsadm resize /dev/VolData01/data01 [size] resize2fs -p /dev/mapper/VolData01-data01 [size] removing lvremove /dev/VolData00/vol01
- 18. THANK YOU ALL