Preface
LVM is the abbreviation of Logical Volume Manager (Logical Volume Manager). It is a mechanism for managing disk partitions in the Linux environment. LVM is a logical layer built on hard disks and partitions to improve disk partition management. Flexibility. As mentioned earlier, LVM is a logical layer added between the disk partition and the file system to shield the lower layer disk partition layout for the file system, provide an abstract disk volume, and establish a file system on the disk volume. Physical volume (physical volume) Physical volume refers to a hard disk partition or a device that logically has the same function as a disk partition (such as RAID). It is the basic storage logical block of LVM, but it is compatible with basic physical storage media (such as partitions, disks, etc.). ) Comparison, but contains management parameters related to LVM.
LVM is a logical layer added between the disk partition and the file system to shield the lower layer disk partition layout for the file system, provide an abstract disk volume, and establish a file system on the disk volume. First we discuss the following LVM terms:
*The physical media (Thephysicalmedia)
Here refers to the storage device of the system: hard disk, which is the lowest storage unit of the storage system.
*Physical volume (physicalvolume)
A physical volume refers to a hard disk partition or a device that has the same function as a disk partition (such as RAID). It is the basic storage logical block of LVM, but compared with basic physical storage media (such as partitions, disks, etc.), it contains Management parameters related to LVM.
*Volume Group (VolumeGroup)
An LVM volume group is similar to a physical hard disk in a non-LVM system, which is composed of physical volumes. One or more "LVM partitions" (logical volumes) can be created on the volume group. The LVM volume group is composed of one or more physical volumes.
*Logical volume (logicalvolume)
LVM logical volumes are similar to hard disk partitions in non-LVM systems, and file systems (such as /home or /usr, etc.) can be established on logical volumes.
*PE (physicalextent)
Each physical volume is divided into basic units called PE (Physical Extents), and a PE with a unique number is the smallest unit that can be addressed by LVM. The size of the PE is configurable and the default is 4MB.
*LE (logicalextent)
Logical volumes are also divided into basic addressable units called LE (Logical Extents). In the same volume group, the size of LE and PE are the same, and there is a one-to-one correspondence.
Experimental part
---------Create logical volume---------
1. Create 2 new partitions, sda5 5G, sd6 10G, after completion as follows
[root@yangcan /]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
Disk identifier: 0x000ed173
Device Boot Start End Blocks Id System
/dev/sda1 * 1 39 307200 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 39 2167 17091584 83 Linux
/dev/sda3 2167 2611 3571712 82 Linux swap / Solaris
/dev/sda4 2611 5221 20966162+ 5 Extended
/dev/sda5 2611 3264 5246528+ 83 Linux
/dev/sda6 3265 4570 10490413+ 83 Linux
2. Initialize sda6 to the physical volume
[root@yangcan /]# pvcreate /dev/sda6
Device vg6 not found (or ignored by filtering).
Writing physical volume data to disk "/dev/sda6"
Physical volume "/dev/sda6" successfully created
3. Create volume group vg6, PE is 16M
[root@yangcan /]# vgcreate -s 16M vg6 /dev/sda6
Volume group "vg6" successfully created
[root@yangcan /]# vgdisplay
--- Volume group ---
VG Name vg6
System ID
Format lvm2
Metadata Areas 1
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 1
Act PV 1
VG Size 10.00 GiB
PE Size 16.00 MiB
Total PE 640
Alloc PE / Size 0/0
Free PE / Size 640 / 10.00 GiB
VG UUID 35tmMm-Hyec-i4f1-xkd7-pMRS-RgRl-sqFa7l
4. Create a logical volume ftpdata with a size of 6G
[root@yangcan /]# lvcreate -L 6G -n ftpdata vg6
Logical volume "ftpdata" created
[root@yangcan /]# lvdisplay
--- Logical volume ---
LV Name /dev/vg6/ftpdata
VG Name vg6
LV UUID LSOtbB-k3mz-DVbb-ATcE-IhBk-V9B7-uaSStM
LV Write Access read/write
LV Status available
# open 0
LV Size 6.00 GiB
Current LE 384
Segments 1
Allocation inherit
Read ahead sectors auto
-currently set to 256
Block device 253:0
5. Format ext4, mount it, and cp some data in
[root@yangcan /]# mke2fs -T ext4 /dev/vg6/ftpdata
[root@yangcan /]# mount /dev/vg6/ftpdata /ftpdata/
[root@yangcan /]# cd /ftpdata/
[root@yangcan ftpdata]# cp /etc/*.conf ./
[root@yangcan ftpdata]# cp /usr/share/dict/linux.words ./
--------Expansion--------
1. Add a new disk to the volume group vg6, and use the remaining sda5 before
[root@yangcan ftpdata]# vgextend vg6 /dev/sda5
Volume group "vg6" successfully extended
[root@yangcan ftpdata]# vgdisplay
--- Volume group ---
VG Name vg6
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 2
Act PV 2
VG Size 15.00 GiB
PE Size 16.00 MiB
Total PE 960
Alloc PE / Size 384 / 6.00 GiB
Free PE / Size 576 / 9.00 GiB
VG UUID 35tmMm-Hyec-i4f1-xkd7-pMRS-RgRl-sqFa7l
2. Expansion of ftpdata, when our files do not increase, expansion is necessary
[root@yangcan ftpdata]# lvextend -L +4G /dev/vg6/ftpdata
Or use it, just to let you understand the difference between -L and -L +. Adding capacity directly after -L means adding to the capacity directly, while -L + capacity means how much capacity is added to the original capacity!
[root@yangcan ftpdata]# lvextend -L 10G /dev/vg6/ftpdata
Extending logical volume ftpdata to 10.00 GiB
Logical volume ftpdata successfully resized
[root@yangcan ftpdata]# lvdisplay
--- Logical volume ---
LV Name /dev/vg6/ftpdata
VG Name vg6
LV UUID LSOtbB-k3mz-DVbb-ATcE-IhBk-V9B7-uaSStM
LV Write Access read/write
LV Status available
# open 1
LV Size 10.00 GiB
Current LE 640
Segments 1
Allocation inherit
Read ahead sectors auto
-currently set to 256
Block device 253:0
[root@yangcan ftpdata]# df -h|grep ftpdata
/dev/mapper/vg6-ftpdata
6.0G 145M 5.5G 3% /ftpdata
At this time, when viewing the capacity of the ftpdata file system, it is still the previous size, so resize2fs is required
[root@yangcan ftpdata]# resize2fs /dev/vg6/ftpdata
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg6/ftpdata is mounted on /ftpdata; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/vg6/ftpdata to 2621440 (4k) blocks.
The filesystem on /dev/vg6/ftpdata is now 2621440 blocks long.
[root@yangcan ftpdata]# df -h|grep ftpdata
/dev/mapper/vg6-ftpdata
9.9G 147M 9.3G 2% /ftpdata
[root@yangcan ftpdata]# lvdisplay
--- Logical volume ---
LV Name /dev/vg6/ftpdata
VG Name vg6
LV UUID LSOtbB-k3mz-DVbb-ATcE-IhBk-V9B7-uaSStM
LV Write Access read/write
LV Status available
# open 1
LV Size 10.00 GiB
Current LE 640
Segments 1
Allocation inherit
Read ahead sectors auto
-currently set to 256
Block device 253:0
Now the file system and logical volume space are consistent
-----------Shrinkage----------
The expansion experiment is finished, and the next step is to reduce the volume.The reduction is more complicated than the expansion, and the size of the reduction cannot be easily specified in normal work.
[root@yangcan ftpdata]# cd ..
[root@yangcan /]# umount /ftpdata/
[root@yangcan /]# e2fsck -f /dev/vg6/ftpdata
e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg6/ftpdata: 41/655360 files (0.0% non-contiguous), 78604/2621440 blocks
Note: We probably shrink to about 6G, then we can't directly resize 2fs to 6G, which is definitely wrong, because PE is the smallest unit that can be addressed by LVM, and the PE size in this experiment is 16M. Let's do the shrink At the time, it is impossible to be 0.6 PE. All pay special attention, a lot of information on the Internet directly specifies the size without testing it!!! It will cause data loss, so when specifying the size, first use lvreduce -t to test. Use bc calculates the position of 6G, which value is suitable in the end
[root@yangcan /]# bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
--6000 is exactly divisible by 16
6000%16
0
--6001 divided by 16 is 1
6001%16
1
5999%16
15
- Exactly 6000M, the remainder is 0, let's compare the difference between 6001 and 6000
[root@yangcan /]# lvreduce -L 6001M /dev/vg6/ftpdata -t
Test mode: Metadata will NOT be updated and volumes will not be (de)activated.
Rounding up size to full physical extent 5.88 GiB
WARNING: Reducing active logical volume to 5.88 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce ftpdata? [y/n]: n
Logical volume ftpdata NOT reduced
A warning message is displayed!
[root@yangcan /]# lvreduce -L 6000M /dev/vg6/ftpdata -t
Test mode: Metadata will NOT be updated and volumes will not be (de)activated.
WARNING: Reducing active logical volume to 5.86 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce ftpdata? [y/n]:
The prompt is 6000M, yes, no problem
When -t test, no problem, then we resize2fs
[root@yangcan /]# resize2fs /dev/vg6/ftpdata 6000M
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/vg6/ftpdata to 1536000 (4k) blocks.
The filesystem on /dev/vg6/ftpdata is now 1536000 blocks long.
Mount, check the size of the file system, it is the latest 6000M, and the data is not lost!!
[root@yangcan /]# mount -a
[root@yangcan /]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 17G 2.1G 14G 14% /
tmpfs 504M 264K 504M 1% /dev/shm
/dev/sda1 291M 31M 246M 11% /boot
/dev/sr0 2.9G 2.9G 0 100% /media/cdrom
/dev/mapper/vg6-ftpdata 5.8G 145M 5.4G 3% /ftpdata
Let's use lvdisplay to see if the size of the logical volume is still 10G
[root@yangcan /]# lvdisplay
--- Logical volume ---
LV Name /dev/vg6/ftpdata
VG Name vg6
LV UUID LSOtbB-k3mz-DVbb-ATcE-IhBk-V9B7-uaSStM
LV Write Access read/write
LV Status available
# open 1
LV Size 10.00 GiB
Current LE 640
Segments 1
Allocation inherit
Read ahead sectors auto
-currently set to 256
Block device 253:0
So we use lvreduce to adjust!
[root@yangcan /]# lvreduce -L 6000M /dev/vg6/ftpdata
WARNING: Reducing active and open logical volume to 5.86 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce ftpdata? [y/n]: n
Logical volume ftpdata NOT reduced
--Prompt that the logical volume is being opened, so we need to stop the logical volume and then adjust the size
[root@yangcan /]# lvchange -an /dev/vg6/ftpdata
[root@yangcan /]# lvscan
inactive'/dev/vg6/ftpdata' [10.00 GiB] inherit
[root@yangcan /]# lvreduce -L 6000M /dev/vg6/ftpdata
Reducing logical volume ftpdata to 5.86 GiB
Logical volume ftpdata successfully resized
[root@yangcan /]# mount -a
mount: special device /dev/vg6/ftpdata does not exist
--When we go to mount, it prompts that there is no such device. So we need to enable
[root@yangcan /]# lvchange -ay /dev/vg6/ftpdata
[root@yangcan /]# lvscan
ACTIVE'/dev/vg6/ftpdata' [5.86 GiB] inherit
Remount, the files inside are still there!
[root@yangcan /]# mount -a
[root@yangcan /]# cd /ftpdata/
[root@yangcan ftpdata]# ll
total 4996
-rw-r--r--. 1 root root 148 Jul 30 19:37 asound.conf
-rw-r--r--. 1 root root 21214 Jul 30 19:37 dnsmasq.conf
-rw-r--r--. 1 root root 559 Jul 30 19:37 dracut.conf
-rw-r--r--. 1 root root 20 Jul 30 19:37 fprintd.conf
-rw-r--r--. 1 root root 0 Jul 30 19:37 gai.conf
-rw-------. 1 root root 781 Jul 30 19:37 grub.conf
-rw-r--r--. 1 root root 9 Jul 30 19:37 host.conf
-rw-r--r--. 1 root root 5309 Jul 30 19:37 kdump.conf
ps: You can also not do the -t test, and directly specify the size to shrink to see if the data is still there?
--------Remove physical volume--------
1. Before removal, there must be no data in the physical volume. Use the following command to check the space size of each physical volume. Plan whether there is enough space to move data!
[root@yangcan Desktop]# pvscan
2. Move the data of the physical volume to be removed to another free physical volume that meets the size
[root@yangcan Desktop]# pvmove /dev/sda6 /dev/sda7
After completion
3. Remove the physical volume from the volume group
[root@yangcan Desktop]#vgchange -an vg5
[root@yangcan Desktop]# vgreduce vg5 /dev/sda6
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