LVM Creates a higher level of abstraction than traditional disk linux partitions. This allows great flexibility in allocating storage.
Logical volumes can be resized and moved b/w physical devicess easily.
Here We can create two partations and toggle it as LVM, The imge showing here is different and use it as a reference,
In order to create a Logical Volume, first we need a
1.Physical Volume, then a
2.Volume Group and
3.Logical Volume
First we need an unpartitioned hard disk /dev/sda. First you need to create physical volumes. To do this you need partitions or a whole disk.
It is possible to run pvcreate command on /dev/sda, but I prefer to use partitions and from partitions I later create physical volumes.
So create two partitions first to create a physical volume.
# fdisk -l
Disk /dev/sda: 22.9 GB, 22922297344 bytes
255 heads, 63 sectors/track, 2786 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 2525 20282031 83 Linux
/dev/sda2 2526 2786 2096482+ 82 Linux swap/Solaris
Creating two Partitions for PV
Two ways we can go here depends upon the partitions you have.If you have more than 3 primary partitions go with extended partition method. If only two primary partition are their you can also create two more and toggle it as lvm. Either ways you can go depends upon your disk partations.
# fdisk -l
Disk /dev/sda: 32.8 GB, 32841072640 bytes
255 heads, 63 sectors/track, 3992 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
Primary partitions have a disadvantage: You only have four of them. (Comes from my earlier days... 64k will always be sufficient... why more that 4 partitions on a 10MB disk?) Therefore, with bigger disks a specific type of primary partition was defined - the "extended partition", which is nothing more than a construct to create
more partitions (itselves sometimes called extended partitions, sometimes "logical drives"). But still the space defined for the "extended partition" (the one in the primary partition table) is valid for the sum of all sub-partitions.
Primary partitions are old-school... I guess nowadays you get away with defining one huge "extended partition" and creating lots of sub-partitions in there. Technically speaking extended partitions take time to scan, since an auto-created sub-partition table is at the beginning of each sub-partition, with a single entry plus a pointer to the next sub-partition... but that's no real show stopper: How often do you need to scan those tables?
If you know that you will have four or less partitions on the disk, stick with simple primary partitions. If unsure, let at least p4 be an extended partition with the remainder of the disk.
# fdisk /dev/sda
The number of cylinders for this disk is set to 3992.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (3447-3992, default 3447):
Using default value 3447
Last cylinder or +size or +sizeM or +sizeK (3447-3992, default 3992):
Using default value 3992
Command (m for help):
Command (m for help): p
Disk /dev/sda: 32.8 GB, 32841072640 bytes
255 heads, 63 sectors/track, 3992 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (3447-3992, default 3447):
Using default value 3447
Last cylinder or +size or +sizeM or +sizeK (3447-3992, default 3992): +600M
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Selected partition 4
First cylinder (3521-3992, default 3521):
Using default value 3521
Last cylinder or +size or +sizeM or +sizeK (3521-3992, default 3992): +500M
Command (m for help): p
Disk /dev/sda: 32.8 GB, 32841072640 bytes
255 heads, 63 sectors/track, 3992 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
/dev/sda3 3447 3520 594405 83 Linux
/dev/sda4 3521 3582 498015 83 Linux
Command (m for help): t
Partition number (1-4): 3
Hex code (type L to list codes): 8e
Changed system type of partition 3 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-4): 4
Hex code (type L to list codes): 8e
Changed system type of partition 4 to 8e (Linux LVM)
Command (m for help): p
Disk /dev/sda: 32.8 GB, 32841072640 bytes
255 heads, 63 sectors/track, 3992 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
/dev/sda3 3447 3520 594405 8e Linux LVM
/dev/sda4 3521 3582 498015 8e Linux LVM
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
# partprobe
# fdisk -l
Disk /dev/sda: 32.8 GB, 32841072640 bytes
255 heads, 63 sectors/track, 3992 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
/dev/sda3 3447 3520 594405 8e Linux LVM
/dev/sda4 3521 3582 498015 8e Linux LVM
Created two new partations and toggled it using LVM. Now create a Physical Volume,
Creating Physical Volume PV
# pvcreate /dev/sda{3,4}
dev_is_mpath: failed to get device for 8:3
Writing physical volume data to disk "/dev/sda3"
Physical volume "/dev/sda3" successfully created
dev_is_mpath: failed to get device for 8:4
Writing physical volume data to disk "/dev/sda4"
Physical volume "/dev/sda4" successfully created
# pvdisplay
"/dev/sda3" is a new physical volume of "580.47 MB"
--- NEW Physical volume ---
PV Name /dev/sda3
VG Name
PV Size 580.47 MB
Allocatable NO
PE Size (KByte) 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID SaxPtr-TI0S-3ITI-0zrh-j9ZB-0xOf-yX76sB
"/dev/sda4" is a new physical volume of "486.34 MB"
--- NEW Physical volume ---
PV Name /dev/sda4
VG Name
PV Size 486.34 MB
Allocatable NO
PE Size (KByte) 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID UXpSUV-auh9-2gDg-IBJ6-UXij-FAid-CNLLdL
OR
# pvs
PV VG Fmt Attr PSize PFree
/dev/sda3 lvm2 a-- 580.47M 580.47M
/dev/sda4 lvm2 a-- 486.34M 486.34M
Now Create a volume group inside the Physical Volume
Creating a Volume Group VG
# vgcreate vg-ctechz /dev/sda{3,4}
Volume group "vg0" successfully created
# vgdisplay
--- Volume group ---
VG Name vg-ctechz
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size 1.04 GB
PE Size 4.00 MB
Total PE 266
Alloc PE / Size 0 / 0
Free PE / Size 266 / 1.04 GB
VG UUID ui4JTr-JOwC-VCvG-5Evc-poOD-3Klr-hM3feq
Or
# vgs
VG #PV #LV #SN Attr VSize VFree
vg-ctechz 2 0 0 wz--n- 1.04G 1.04G
We can create a volume group with fixed size as well,
Ex: vgcreate -s +PESize vgname /dev/sda3 /dev/sda4
Now Create a Logical Volume
Creating Logical Volume LV
lvcreate -L +600 -n lvmName /dev/vgName
# lvcreate -L +600 -n lvm-ctechz /dev/vg-ctechz
Logical volume "lvm-sda" created
# lvdisplay
--- Logical volume ---
LV Name /dev/vg-ctechz/lvm-ctechz
VG Name vg-ctechz
LV UUID jZEuoN-16MG-30eX-SZaI-8ETO-ZguH-YRVyeN
LV Write Access read/write
LV Status available
# open 0
LV Size 600.00 MB
Current LE 150
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
OR
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
lvm-ctechz vg-ctechz -wi-a- 600.00M
Now format the LVM Volume with the needed file system and mounted in the drive,
# mkdir /lvm-ctechz
# mkfs.ext3 /dev/vg-ctechz/lvm-ctechz
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
76800 inodes, 153600 blocks
7680 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=159383552
5 block groups
32768 blocks per group, 32768 fragments per group
15360 inodes per group
Superblock backups stored on blocks: 32768, 98304
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 36 mounts
or 180 days, whichever comes first.Use tune2fs -c or -i to override.
Mount it in fstab
# Vim /etc/fstab
/dev/vg-ctechz/lvm-ctechz /lvm-ctechz ext3 defaults 0 0
# mount -a
# mount/dev/sda1 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
/dev/mapper/vg0-lvm--sda on /LVM type ext3 (rw)
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 25G 4.4G 20G 19% /
tmpfs 593M 0 593M 0% /dev/shm
/dev/mapper/vg--ctechz-lvm--ctechz
591M 17M 545M 3% /lvm-ctechz
# fdisk -l
Disk /dev/sda: 31.8 GB, 31890341888 bytes
255 heads, 63 sectors/track, 3877 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3315 26627706 83 Linux
/dev/sda2 3316 3446 1052257+ 82 Linux swap/Solaris
/dev/sda3 3447 3520 594405 8e Linux LVM
/dev/sda4 3521 3582 498015 8e Linux LVM
Create a big file and put it in mounted lvm dir the test another scenario's
# dd if=/dev/zero of=lvm-sizefile bs=1000024 count=500
Created some files to put in lvm volume
