LVM

Logical Volume Manager

Written by Zak Zhu

参考

• 马哥linux视频
• RHCE培训(rh133-unit13)

LVM

LVM依赖于内核Device Mapper模块

LV设备文件: /dev/mapper/VG_NAME-LV_NAME

• A layer of abstraction that allows easy manipulation of volumes
• Supports resizing of filesystems
• Allows filesystems to span multiple physical devices

• Block devices are designated as Physical Volumes
• One or more Physical Volumes are used to created a Volume Group
• Volume Groups are defined with Physical Extents of a fixed size
• Logical Volumes are composed of Physical Extents from Volume Group
• Filesystems may be created on Logical Volumes

yum install lvm2 -y # 安装lvm2

PV相关命令

• pvcreate

  pvcreate /dev/PHYSICAL_PARTION

  

• pvs & pvdisplay

  pvs               # 简要显示
  pvdisplay     # 详细显示

  

  

• pvremove

  pvremove /dev/PHYSICAL_PATIONS

• pvmove

  pvmove SRC_PV DEST_PV

• pvscan

  pvscan            # scan all disks for physical volumes

  

VG相关命令

PE默认大小: 4M

• vgcreate

  vgcreate [-s PE_SIZE[bBkKmMgG]] VG_NAME PV_NAME

  

• vgs & vgdisplay

  vgs           # 简要显示
  vgdisplay     # 详细显示

  

  

• vgchange

  vgchange -s PE_SIZE[bBkKmMgG]         # 修改PE的大小

• vgremove

  vgremove VG_NAME

• vgextend

  vgextend VG_NAME PV_NAME

  

• vgreduce

  务必先考虑pvmove迁移数据, 再vgreduce

  vgreduce VG_NAME PV_NAME

• vgscan

  vgscan            # scan all disks for volume groups and rebuild caches

LV相关命令

• lvcreate

  lvcreate -L LV_SIZE[mMgGtT] -n LV_NAME VG_NAME 

  

• lvs & lvdisplay

  

  

• lvremove

  lvremove /dev/mapper/VG_NAME-LV_NAME

  

• lvscan

  lvscan            # scan all disks for Logical Volumes

扩展LV

1. 查看所属的VG是否有足够的剩余空间

   vgs

   

2. *卸载要扩展的LV

   umount /dev/mapper/vg0-lv_data

3. *强制检查要扩展的LV的文件系统

   e2fsck -f /dev/mapper/vg0-lv_data

4. 扩展LV的大小

   lvextend -L +1G /dev/mapper/vg0-lv_data

   

5. 扩展文件系统的范围

   resize2fs /dev/mapper/vg0-lv_data

   

6. *挂载已扩展的LV

   mount -a

   

缩减LV

危险警告: 尽量不要做缩减LV !!

1. 一定要先卸载LV

   umount /dev/mapper/vg0-lv_data

2. 强制检查要缩减的LV的文件系统

   e2fsck -f /dev/mapper/vg0-lv_data

   

3. 缩减LV的文件系统的范围

   resize2fs /dev/mapper/vg0-lv_data 1G

   

4. 缩减LV的大小

   强烈建议: 缩减后的LV大小要求略大于缩减后的文件系统大小 !!!

   lvreduce -L 1.2G /dev/mapper/vg0-lv_data

   

5. 挂载已缩减的LV

   mount -a

   

LVM快照

• Snapshots are special Logical Volumes
• Snapshots are perfect for bacups where a temporary copy of an existing dataset is needed
• Snapshots only consume space where they are different from the original Logical Volume

使用快照

1. 创建快照

   lvcreate -L 200M -s -n snap_data /dev/mapper/vg0-lv_data

   

2. 挂载快照

   mount -o ro /dev/mapper/vg0-snap_data /mnt/snap_data

   

3. 压缩备份

   tar -Jpcv -f snap_data$(date +"%Y%m%d-%H%M").txz /mnt/snap_data/*

   

4. 卸载删除

   umount /dev/mapper/vg0-snap_data

   lvremove /dev/mapper/vg0-snap_data