{"id":713,"date":"2012-07-13T15:49:20","date_gmt":"2012-07-13T07:49:20","guid":{"rendered":"http:\/\/rmohan.com\/?p=713"},"modified":"2014-05-29T11:21:26","modified_gmt":"2014-05-29T03:21:26","slug":"lvm-in-linux","status":"publish","type":"post","link":"https:\/\/mohan.sg\/?p=713","title":{"rendered":"LVM in linux"},"content":{"rendered":"

LVM in linux<\/p>\n

<\/div>\n
\n
Logical Volume Management[LVM]<\/p>\n
LVM\u00a0is a\u00a0logical volume manager\u00a0for the\u00a0Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. The term “volume” refers to a disk drive or partition.
\nEvery system contains\u00a0Physical Volums[PV]<\/strong>. Such as hard disks, partitions or external storages. Volume management treats\u00a0PV<\/strong>s as sequences of chunks called\u00a0Physical<\/strong>\u00a0Extents<\/strong>\u00a0(PEs)<\/strong>. There is an another concept also.\u00a0Logical Extents(LE)<\/strong>. Each\u00a0LE\u00a0<\/strong>maps one-to-one\u00a0PE<\/strong>. The system pools\u00a0LE<\/strong>s into a\u00a0Volume Group (VG)<\/strong>. We can extend this\u00a0VG<\/strong>\u00a0by adding a group of\u00a0Logical extents<\/strong>\u00a0to it from anywhere at anytime.<\/div>\n
Uses of LVM:<\/strong><\/p>\n
    \n
  1. Extending the partitions online<\/li>\n
  2. Grouping of hard disks<\/li>\n
  3. Reducing the partitions \/ hard dsik size (offline)<\/li>\n
  4. Increasing the performance<\/li>\n
  5. Taking Backup (SNAPSHOT)<\/li>\n<\/ol>\n<\/div>\n
    Example:<\/strong><\/div>\n
    Here we are going to discuss a\u00a0Volume Group(VG)<\/strong>\u00a0created from 3Physical Voumes(PV)<\/strong>. And in that\u00a0VG<\/strong>\u00a0we’ll create two\u00a0Logival Volumes(LV)\u00a0<\/strong>And mount it to\u00a0\/linux1<\/strong>\u00a0and\u00a0\/linux2\u00a0<\/strong>respectively.<\/div>\n
    Now first of all in our example, we have 3 partitions. In real industry it may be 3 different hard disks.<\/div>\n
    Let it be (1)\u00a0\/dev\/sda5<\/strong>\u00a0(2)\u00a0\/dev\/sda6<\/strong>\u00a0(3)\u00a0\/dev\/sda7\u00a0<\/strong>each of size300Mb<\/strong>.<\/div>\n
    [root@vm4 ~]# fdisk -l<\/strong><\/div>\n
    \/dev\/sda5 429 465 297171 8e Linux LVM<\/strong><\/div>\n
    \/dev\/sda6 466 502 297171 8e Linux LVM<\/strong><\/div>\n
    \/dev\/sda7 503 539 297171 8e Linux LVM<\/strong><\/div>\n

    \n<\/strong>
    \nSteps:<\/strong><\/div>\n
    First we will convert this partions(hard disks) into\u00a0Physical Volumes(PV).<\/strong>Then we’ll create a\u00a0Volume Group (VG)\u00a0<\/strong>from those\u00a0PV s.<\/strong>\u00a0Then inside that\u00a0VG,\u00a0<\/strong>We’ll create two\u00a0Logical Volumes (LV)\u00a0<\/strong>and we’ll mount those for use.<\/div>\n
    Step1: Creating Physical Volume(PV)s.<\/span><\/strong><\/div>\n
    Partitions or disks can be converted into\u00a0PV s<\/strong>\u00a0using the following Command.<\/div>\n
    #pvcreate PARTITION_NAMES<\/strong><\/div>\n
    #pvcreate \/dev\/sda5 \/dev\/sda6 \/dev\/sda7<\/strong><\/div>\n
    or as below<\/div>\n
    #pvcreate \/dev\/sda{5,6,7}<\/strong><\/div>\n
    <\/div>\n
    [root@vm4 ~]# pvcreate \/dev\/sda5 \/dev\/sda6 \/dev\/sda7<\/strong><\/div>\n
    Physical volume “\/dev\/sda5” successfully created<\/strong><\/div>\n
    Physical volume “\/dev\/sda6” successfully created<\/strong><\/div>\n
    Physical volume “\/dev\/sda7” successfully created<\/strong><\/div>\n
    \u00a0<\/strong><\/div>\n
    Monitoring or verifying the PV s:<\/strong><\/div>\n
    You can verify the\u00a0PV s<\/strong>\u00a0using following commands,<\/div>\n
    #pvscan<\/strong><\/div>\n
    #pvdisplay<\/strong><\/div>\n
    #pvs<\/strong><\/div>\n
    [root@vm4 ~]# pvs<\/strong><\/div>\n
    PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
    \/dev\/sda5 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
    \/dev\/sda6 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
    \/dev\/sda7 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
    <\/div>\n
    Step2: Creating Volume Group(VG):<\/strong><\/span><\/div>\n
    The\u00a0Physical Volumes\u00a0<\/strong>are grouped into one to make it a\u00a0Volume Group(VG).\u00a0<\/strong>It can be done using the following command.<\/div>\n
    #vgcreate VG_NAME PV_NAMES<\/strong><\/div>\n
    #vgcreate oracle \/dev\/sda5 \/dev\/sda6 \/dev\/sda7<\/strong><\/div>\n
    or as below<\/div>\n
    #vgcreate oracle \/dev\/sda{5,6,7}<\/strong><\/div>\n
    <\/div>\n
    It will have a appoximate size of\u00a0900(300+300+300).<\/strong>\u00a0Some part will for writing headers LE and making LE-PE mapping.<\/div>\n
    [root@vm4 ~]# vgcreate oracle \/dev\/sda5 \/dev\/sda6 \/dev\/sda7<\/strong><\/div>\n
    Volume group “oracle” successfully created<\/strong><\/div>\n
    [root@vm4 ~]# vgs<\/strong><\/div>\n
    VG #PV #LV #SN Attr VSize VFree<\/strong><\/div>\n
    oracle 3 0 0 wz–n- 864.00M 864.00M<\/strong><\/div>\n
    <\/div>\n
    \u00a0<\/strong><\/div>\n
    Monitoring or verifying the VG s:<\/strong><\/div>\n
    You can verify the\u00a0VG s<\/strong>\u00a0using following commands,<\/div>\n
    #vgscan<\/strong><\/div>\n
    #vgdisplay<\/strong><\/div>\n
    #vgs<\/strong><\/div>\n
    Output of #vgs is shown above the picture.<\/div>\n
    <\/div>\n
    Step3: Creating Logical Volumes In Volume Group:<\/strong><\/span><\/div>\n
    Now we got a volume group “Oracle<\/strong>” of size as the total size of all individual disks\/partitions. Now we can create\u00a0Logical Volumes\u00a0<\/strong>or usable partitions inside it. We will create two logical Volumes\u00a0lvm1<\/strong>\u00a0and\u00a0lvm2<\/strong>\u00a0of size\u00a0100Mb<\/strong>\u00a0each.<\/div>\n
    <\/div>\n
    The lvm1 and lvm2 can be created using the following commands.<\/div>\n
    #lvcreate -L SIZE -n LV_NAME VG_NAME<\/strong><\/div>\n
    #lvcreate -L 100M -n lvm1 oracle<\/strong><\/div>\n
    #lvcreate -L 100M -n lvm1 oracle<\/strong><\/div>\n
    [root@vm4 ~]# lvcreate -L 100M -n lvm1 oracle<\/strong><\/div>\n
    Logical volume “lvm1” created<\/strong><\/div>\n
    [root@vm4 ~]# lvcreate -L 100M -n lvm2 oracle<\/strong><\/div>\n
    Logical volume “lvm2” created<\/strong><\/div>\n
    <\/div>\n
    \u00a0<\/strong><\/div>\n
    Monitoring or verifying the LV s:<\/strong><\/div>\n
    You can verify the\u00a0LV s<\/strong>\u00a0using following commands,<\/div>\n
    #lvscan<\/strong><\/div>\n
    #lvdisplay<\/strong><\/div>\n
    #lvs<\/strong><\/div>\n
    [root@vm4 ~]# lvs<\/strong><\/div>\n
    LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
    lvm1 oracle -wi-a- 100.00M<\/strong><\/div>\n
    lvm2 oracle -wi-a- 100.00M<\/strong><\/div>\n
    The Logical Voumes lvm1 and lvm2 should be formatted(making filesystem in those) before mounting it. Then only you can use those partitions.<\/div>\n
    Here formatting in ext3:<\/div>\n
    #mkfs.ext3 \/dev\/oracle\/lvm1<\/strong><\/div>\n
    #mkfs.ext3 \/dev\/oracle\/lvm2<\/strong><\/div>\n
    Making Mount Points:<\/div>\n
    #mkdir \/linux1<\/strong><\/div>\n
    #mkdir \/linux2<\/strong><\/div>\n
    <\/div>\n
    Mounting (Temporary):<\/div>\n
    #mount \/dev\/oracle\/lvm1 \/linux1<\/strong><\/div>\n
    #mount \/dev\/oracle\/lvm2 \/linux2<\/strong><\/div>\n
    \u00a0\u00a0<\/strong><\/div>\n
    [root@vm4 ~]# mount<\/strong><\/div>\n
    [Output truncated]<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm1 on \/linux1 type ext3 (rw)<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm2 on \/linux2 type ext3 (rw)<\/strong><\/div>\n
    <\/div>\n
    Extending a Logical Volume (Online):<\/strong><\/span><\/div>\n
    <\/div>\n
    Now We have a Volume group “oracle” of size about 900Mb. And two Logical vloumes lvm1 and lvm2 mounted on \/linux1 and \/linux2 respectively. Each having 100Mb size. Now we’ll extend the size of lvm1 by 100Mb.<\/div>\n
    Extending size of a LV can be done online, That is by keeping them mounted. It can be achived by executing following command.<\/div>\n
    #lvextend -L +SIZE THE_PATH_OF_LV<\/strong><\/div>\n
    #lvextend -L +100M \/dev\/oracle\/lvm1<\/strong><\/div>\n
    <\/div>\n
    Before:<\/strong><\/div>\n
    [root@vm4 ~]# lvs<\/strong><\/div>\n
    LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
    lvm1 oracle -wi-ao\u00a0100.00M<\/strong><\/div>\n
    lvm2 oracle -wi-ao 100.00M<\/strong><\/div>\n
    <\/div>\n
    Executing:<\/strong><\/div>\n
    [root@vm4 ~]# lvextend -L +100M \/dev\/oracle\/lvm1<\/strong><\/div>\n
    Extending logical volume lvm1 to 200.00 MB<\/strong><\/div>\n
    Logical volume lvm1 successfully resized<\/strong><\/div>\n
    <\/div>\n
    After:<\/strong><\/div>\n
    [root@vm4 ~]# lvs<\/strong><\/div>\n
    LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
    lvm1 oracle -wi-ao\u00a0200.00M<\/strong><\/div>\n
    lvm2 oracle -wi-ao 100.00M<\/strong><\/div>\n
    After executing above commands you can verify the changed size by any of following commands<\/div>\n
    #lvs, #lvdisplay, #lvscan<\/strong><\/div>\n
    But if you check<\/div>\n
    #df -hT<\/strong><\/div>\n
    it will be showing the old size only. Because the filesystem is updated the changed in Logical Volume. It can be updated by following command.<\/div>\n
    #resize2fs \/dev\/oracle\/lvm1<\/strong><\/div>\n
    NOTE: In case of extending the LV is resized first and the filesystem after that. But in case of shrinking a LV, filesystem is shrinked first followed by the shrink in LV.<\/strong><\/div>\n
    Before:<\/strong><\/div>\n
    [root@vm4 ~]# df -hT<\/strong><\/div>\n
    Filesystem Type Size Used Avail Use% Mounted on<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm1<\/strong><\/div>\n
    ext3\u00a097M\u00a05.6M\u00a087M 7% \/linux1<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm2<\/strong><\/div>\n
    ext3 97M 5.6M 87M 7% \/linux2<\/strong><\/div>\n
    <\/div>\n
    Executing:<\/strong><\/div>\n
    [root@vm4 ~]# resize2fs \/dev\/oracle\/lvm1<\/strong><\/div>\n
    resize2fs 1.39 (29-May-2006)<\/strong><\/div>\n
    Filesystem at \/dev\/oracle\/lvm1 is mounted on \/linux1; on-line resizing required<\/strong><\/div>\n
    Performing an on-line resize of \/dev\/oracle\/lvm1 to 204800 (1k) blocks.<\/strong><\/div>\n
    The filesystem on \/dev\/oracle\/lvm1 is now 204800 blocks long.<\/strong><\/div>\n
    <\/div>\n
    After:<\/strong><\/div>\n
    [root@vm4 ~]# df -hT<\/strong><\/div>\n
    Filesystem Type Size Used Avail Use% Mounted on<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm1<\/strong><\/div>\n
    ext3\u00a0194M\u00a05.6M\u00a0179M 4% \/linux1<\/strong><\/div>\n
    \/dev\/mapper\/oracle-lvm2<\/strong><\/div>\n
    ext3 97M 5.6M 87M 7% \/linux2<\/strong><\/div>\n
    <\/div>\n
    Shrinking a Logical Volume (Offline):<\/strong><\/div>\n
    As we extended the size of Logical Volume, we can reduce the size also. But in later case, it can be done only offline. That is the LV should be unmounted for reducing its size.<\/div>\n
    <\/div>\n
    For Shrinking a Volume:<\/strong><\/p>\n
      \n
    1. Filesystem must be reduced first<\/li>\n
    2. Requires a filesystem check and cannot be performed online<\/li>\n
    3. #lvreduce can then reduce the volume<\/li>\n<\/ol>\n<\/div>\n
      Now We have a Volume group “oracle” of size about 900Mb. And two Logical vloumes lvm1 and lvm2 mounted on \/linux1 and \/linux2 respectively. Size of lvm1 is 200Mb and size of lvm2 is 100Mb. Now we’ll reduce the size of lvm2 by 40Mb.<\/div>\n
      Current status:<\/div>\n
      [root@vm4 ~]# lvs<\/strong><\/div>\n
      LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
      lvm1 oracle -wi-ao 200.00M<\/strong><\/div>\n
      lvm2 oracle -wi-ao 100.00M<\/strong><\/div>\n
      <\/div>\n
      Step1: Unmont the volume:<\/strong><\/div>\n
      #umount \/linux2<\/strong><\/div>\n
      <\/div>\n
      Step2: Checking the filesystem:<\/strong><\/div>\n
      #e2fsck -f LV_Path<\/strong><\/div>\n
      #fsck -f \/dev\/oracle\/lvm2<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# e2fsck -f \/dev\/oracle\/lvm2<\/strong><\/div>\n
      e2fsck 1.39 (29-May-2006)<\/strong><\/div>\n
      Pass 1: Checking inodes, blocks, and sizes<\/strong><\/div>\n
      Pass 2: Checking directory structure<\/strong><\/div>\n
      Pass 3: Checking directory connectivity<\/strong><\/div>\n
      Pass 4: Checking reference counts<\/strong><\/div>\n
      Pass 5: Checking group summary information<\/strong><\/div>\n
      \/dev\/oracle\/lvm2: 11\/25688 files (9.1% non-contiguous), 8914\/102400 blocks<\/strong><\/div>\n
      This is to make sure that the filesystem is in a consistent state.<\/div>\n
      <\/div>\n
      Step3: Resizing the filesystem:<\/strong><\/div>\n
      #resize2fs LV_Path Final_size<\/strong><\/div>\n
      #resize2fs \/dev\/oracle\/lvm2 60M<\/strong><\/div>\n
      [Total size was 100Mb. Reduction 40Mb. So final size is 100-40=60]<\/div>\n
      <\/div>\n
      [root@vm4 ~]# resize2fs \/dev\/oracle\/lvm2 60M<\/strong><\/div>\n
      resize2fs 1.39 (29-May-2006)<\/strong><\/div>\n
      Resizing the filesystem on \/dev\/oracle\/lvm2 to 61440 (1k) blocks.<\/strong><\/div>\n
      The filesystem on \/dev\/oracle\/lvm2 is now 61440 blocks long.<\/strong><\/div>\n
      <\/div>\n
      Step4: Now reduce the LV using #lvreduce<\/strong><\/div>\n
      #lvreduce -L Size LV_Path<\/strong><\/div>\n
      #lvreduce -L 60M \/dev\/oracle\/lvm2<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# lvreduce -L 60M \/dev\/oracle\/lvm2<\/strong><\/div>\n
      WARNING: Reducing active logical volume to 60.00 MB<\/strong><\/div>\n
      THIS MAY DESTROY YOUR DATA (filesystem etc.)<\/strong><\/div>\n
      Do you really want to reduce lvm2? [y\/n]: y<\/strong><\/div>\n
      Reducing logical volume lvm2 to 60.00 MB<\/strong><\/div>\n
      Logical volume lvm2 successfully resized<\/strong><\/div>\n
      <\/div>\n
      Before Reducing:<\/strong><\/div>\n
      root@vm4 ~]# lvs<\/strong><\/div>\n
      LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
      lvm1 oracle -wi-ao 200.00M<\/strong><\/div>\n
      lvm2 oracle -wi-ao\u00a0100.00M<\/strong><\/div>\n
      <\/div>\n
      After Reducing:<\/strong><\/div>\n
      [root@vm4 ~]# lvs<\/strong><\/div>\n
      LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong><\/div>\n
      lvm1 oracle -wi-ao 200.00M<\/strong><\/div>\n
      lvm2 oracle -wi-a-\u00a060.00M<\/strong><\/div>\n
      <\/div>\n
      After mounting:<\/strong><\/div>\n
      [root@vm4 ~]# df -hT<\/strong><\/div>\n
      <\/div>\n
      \/dev\/mapper\/oracle-lvm1\u00a0<\/strong>ext3 194M 5.6M 179M 4% \/linux1<\/strong><\/div>\n
      \/dev\/mapper\/oracle-lvm2\u00a0<\/strong>ext3\u00a059M\u00a05.3M 50M 10% \/linux2<\/strong><\/div>\n
      <\/div>\n
      Adding a Pysical Volume to a VG:<\/strong><\/div>\n
      <\/div>\n
      Now we have a Volume Group “oracle” of size 900Mb. Suppose we used upto the maximum usable size. So we need to extend the size of the VG.<\/div>\n
      In this case we will create a new partition\/a new hard disk, and will make it a Physical Volume and add it to the Volume group.<\/div>\n
      Current status:<\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV\u00a0#LV #SN Attr VSize VFree<\/strong><\/div>\n
      oracle\u00a03\u00a02 0 wz–n- 864.00M 624.00M<\/strong><\/div>\n
      <\/div>\n
      Now we created one more partition with id LVM.<\/div>\n
      \/dev\/sda5 429 465 297171 8e Linux LVM<\/strong><\/div>\n
      \/dev\/sda6 466 502 297171 8e Linux LVM<\/strong><\/div>\n
      \/dev\/sda7 503 539 297171 8e Linux LVM<\/strong><\/div>\n
      \/dev\/sda8 540 576 297171 8e Linux LVM<\/strong><\/div>\n
      <\/div>\n
      Step1:<\/strong><\/div>\n
      First we have to convert it to physical volume.<\/div>\n
      #pvcreate \/dev\/sda8<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvcreate \/dev\/sda8<\/strong><\/div>\n
      Physical volume “\/dev\/sda8” successfully created<\/strong><\/div>\n
      <\/div>\n
      Current status of all Physical Volumes:<\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 oracle lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda6 oracle lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 oracle lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda8 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
      See \/dev\/sda8 is not the part of the VG oracle<\/div>\n
      <\/div>\n
      Step2:<\/strong><\/div>\n
      Now we will add the PV \/dev\/sda8 to Volume Group “oracle”<\/div>\n
      <\/div>\n
      #vgextend -v oracle \/dev\/sda8<\/strong><\/div>\n
      [ -v is for verbose. To see what is happening]<\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgextend -v oracle \/dev\/sda8<\/strong><\/div>\n
      Checking for volume group “oracle”<\/strong><\/div>\n
      Archiving volume group “oracle” metadata (seqno 5).<\/strong><\/div>\n
      Wiping cache of LVM-capable devices<\/strong><\/div>\n
      Adding physical volume ‘\/dev\/sda8’ to volume group ‘oracle’<\/strong><\/div>\n
      Volume group “oracle” will be extended by 1 new physical volumes<\/strong><\/div>\n
      Creating volume group backup “\/etc\/lvm\/backup\/oracle” (seqno 6).<\/strong><\/div>\n
      Volume group “oracle” successfully extended<\/strong><\/div>\n
      <\/div>\n
      After extending the VG with new Physical Volume:<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV\u00a0#LV #SN Attr Vsize VFree<\/strong><\/div>\n
      oracle\u00a04\u00a02 0 wz–n-\u00a01.12G 912.00M<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 oracle lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda6 oracle lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 oracle lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda8\u00a0oracle\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      <\/div>\n
      Now \/dev\/sda8 became a part of VG oracle.<\/div>\n
      <\/div>\n
      Removing a Pysical volume form a VG:<\/strong><\/div>\n
      Before removing a physical volume from a volume group, you can make sure that the physical volume is not used by any logical volumes by using the\u00a0#<\/strong>pvdisplay<\/strong><\/code>\u00a0command. If the physical volume is still being used you will have to migrate the data to another physical volume using the#<\/strong>pvmove<\/strong><\/code>\u00a0command. Then use the\u00a0vgreduce<\/code>\u00a0command to remove the physical volume.<\/div>\n
      <\/div>\n
      Current status of Pysical Volumes:<\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 oracle lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda6 oracle lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 oracle lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda8 oracle lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      In this example we will remove the Pysical Volume \/dev\/sda5 in which some Physical Extents are already used by some LV. So They need to be migrated.<\/div>\n
      <\/div>\n
      The status of \/dev\/sds5 is<\/div>\n
      [root@vm4 ~]# pvdisplay \/dev\/sda5<\/strong><\/div>\n
      — Physical volume —<\/strong><\/div>\n
      PV Name \/dev\/sda5<\/strong><\/div>\n
      VG Name oracle<\/strong><\/div>\n
      PV Size 290.21 MB \/ not usable 2.21 MB<\/strong><\/div>\n
      Allocatable yes<\/strong><\/div>\n
      PE Size (KByte) 4096<\/strong><\/div>\n
      Total PE 72<\/strong><\/div>\n
      Free PE 22<\/strong><\/div>\n
      Allocated PE 50<\/strong><\/div>\n
      PV UUID 9l5HlF-h8Of-2J6D-TDr4-BY34-cREh-7U5zxm<\/strong><\/div>\n
      Step1:<\/strong><\/div>\n
      Migrate the used Pes using\u00a0#pvmove<\/strong>\u00a0command<\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvmove -v \/dev\/sda5<\/strong><\/div>\n
      Finding volume group “oracle”<\/strong><\/div>\n
      Archiving volume group “oracle” metadata (seqno 6).<\/strong><\/div>\n
      [output truncated]<\/strong><\/div>\n
      Creating volume group backup “\/etc\/lvm\/backup\/oracle” (seqno 9).<\/strong><\/div>\n
      <\/div>\n
      Step2:<\/strong><\/div>\n
      Now reduce the Volume Group size by command\u00a0#vgreduce<\/strong><\/div>\n
      #vgreduce VG_name Removing_PV_Path<\/strong><\/div>\n
      #vgreduce oracle \/dev\/sda5<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgreduce oracle \/dev\/sda5<\/strong><\/div>\n
      Removed “\/dev\/sda5” from volume group “oracle”<\/strong><\/div>\n
      After Remvoing PV:<\/strong><\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV\u00a0#LV #SN Attr\u00a0VSize\u00a0VFree<\/strong><\/div>\n
      oracle\u00a03\u00a02 0 wz–n-\u00a0864.00M\u00a0624.00M<\/strong><\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 lvm2 — 290.21M 290.21M\u00a0\/Now not part of\u00a0oracle\u00a0VG<\/strong><\/div>\n
      \/dev\/sda6 oracle lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 oracle lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda8 oracle lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      <\/div>\n
      Merging two Volume Groups:<\/strong><\/span><\/div>\n
      Two different Volume Groups can be merged to a single Volume Group.<\/div>\n
      Suppose we have two VGs “oracle” and “linux”.<\/div>\n
      Current status of VGs are:<\/strong><\/div>\n
      VG #PV #LV #SN Attr VSize VFree<\/strong><\/div>\n
      linux 1 0 0 wz–n- 288.00M 288.00M<\/strong><\/div>\n
      oracle 3 2 0 wz\u2014n- 864.00M 624.00M<\/strong><\/div>\n
      <\/div>\n
      Now we are going to merge “oracle” and “linux” to get a single VG linux.<\/div>\n
      We are using the command\u00a0#vgmerge<\/strong>\u00a0for this.<\/div>\n
      #vgmerge\u00a0<\/strong>merges two existing volume groups. The inactive SourceVolumeGroupName will be merged into the DestinationVolumeGroupName if physical extent sizes are equal and physical and logical volume summaries of both volume groups fit into DestinationVolumeGroupName’s limits.<\/div>\n
      <\/div>\n
      #vgmerge -v databases my_vg<\/strong><\/div>\n
      merges the inactive volume group named “my_vg” into the active or inactive volume group named “databases” giving verbose runtime information.<\/div>\n
      Step1:<\/strong><\/div>\n
      we are going to merge “oracle” and “linux” to get a single VG linux.<\/div>\n
      Make the source Volume Group inactive. In this case source is oracle.<\/div>\n
      #vgchange -a n oracle<\/div>\n
      umount the LV which uses the oracle VG then only u can inactivate it.<\/div>\n
      <\/div>\n
      [root@vm4 ~]# umount \/linux1<\/strong><\/div>\n
      [root@vm4 ~]# umount \/linux2<\/strong><\/div>\n
      [root@vm4 ~]# vgchange -a n oracle<\/strong><\/div>\n
      0 logical volume(s) in volume group “oracle” now active<\/strong><\/div>\n
      <\/div>\n
      #vgmerge Destination Source<\/strong><\/div>\n
      we are going to merge “oracle” and “linux” to get a single VG linux. So<\/div>\n
      #vgmaerge -v linux oracle<\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgmerge -v linux oracle<\/strong><\/div>\n
      Checking for volume group “linux”<\/strong><\/div>\n
      Checking for volume group “oracle”<\/strong><\/div>\n
      Archiving volume group “oracle” metadata (seqno 10).<\/strong><\/div>\n
      Archiving volume group “linux” metadata (seqno 1).<\/strong><\/div>\n
      Writing out updated volume group<\/strong><\/div>\n
      Creating volume group backup “\/etc\/lvm\/backup\/linux” (seqno 2).<\/strong><\/div>\n
      Volume group “oracle” successfully merged into “linux”<\/strong><\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV #LV #SN Attr VSize VFree<\/strong><\/div>\n
      linux\u00a04\u00a02 0 wz–n- 1.12G\u00a0912.00M<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgchange -a y linux<\/strong><\/div>\n
      2 logical volume(s) in volume group “linux” now active<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# mount \/dev\/linux\/lvm1 \/linux1<\/strong><\/div>\n
      [root@vm4 ~]# mount \/dev\/linux\/lvm2 \/linux2<\/strong><\/div>\n
      [root@vm4 ~]# mount<\/strong><\/div>\n
      [output truncated]<\/strong><\/div>\n
      \/dev\/mapper\/linux-lvm1 on \/linux1 type ext3 (rw)<\/strong><\/div>\n
      \/dev\/mapper\/linux-lvm2 on \/linux2 type ext3 (rw)<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
      \/dev\/sda6\u00a0linux\u00a0lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7\u00a0linux\u00a0lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda8\u00a0linux\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda9\u00a0linux\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      <\/div>\n
      Spliting a Volume Group into two:<\/strong><\/span><\/div>\n
      We can split a Volume Group into two Volume Groups using the command\u00a0#vgsplit<\/strong><\/div>\n
      We have one VG\u00a0oracle<\/strong>\u00a0with 4 PVs. We will split that VG oracle to oracle and another VG\u00a0redhat<\/strong>. The PVs\u00a0\/dev\/sda8<\/strong>\u00a0and\u00a0\/dev\/sda9<\/strong>\u00a0will be moved to redhat.<\/div>\n
      The syntax is as follows:<\/div>\n
      #vgsplit EXISTING_VG NEW_VG PATH OF PVs_TO _BE_MOVED<\/strong><\/div>\n
      #vgsplit oracle redhat \/dev\/sda8 \/dev\/sda9<\/strong><\/div>\n
      [root@vm4 ~]# vgsplit linux redhat \/dev\/sda8 \/dev\/sda9<\/strong><\/div>\n
      New volume group “redhat” successfully split from “linux”<\/strong><\/div>\n
      <\/div>\n
      Before:<\/strong><\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV #LV #SN Attr VSize VFree<\/strong><\/div>\n
      linux\u00a04\u00a02 0 wz–n- 1.12G 912.00M<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
      \/dev\/sda6 linux lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 linux lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda8 linux\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda9 linux<\/strong>\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      <\/div>\n
      After:<\/strong><\/div>\n
      [root@vm4 ~]# vgs<\/strong><\/div>\n
      VG #PV #LV #SN Attr VSize VFree<\/strong><\/div>\n
      linux 2 2 0 wz–n- 576.00M 336.00M<\/strong><\/div>\n
      redhat 2\u00a00 0 wz–n- 576.00M 576.00M<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvs<\/strong><\/div>\n
      PV VG Fmt Attr PSize PFree<\/strong><\/div>\n
      \/dev\/sda5 lvm2 — 290.21M 290.21M<\/strong><\/div>\n
      \/dev\/sda6 linux lvm2 a- 288.00M 248.00M<\/strong><\/div>\n
      \/dev\/sda7 linux lvm2 a- 288.00M 88.00M<\/strong><\/div>\n
      \/dev\/sda8 redhat\u00a0lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      \/dev\/sda9 redhat\u00a0<\/strong>lvm2 a- 288.00M 288.00M<\/strong><\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgchange -a y linux<\/strong><\/div>\n
      2 logical volume(s) in volume group “linux” now active<\/strong><\/div>\n
      [root@vm4 ~]# vgchange -a y redhat<\/strong><\/div>\n
      \n
      0 logical volume(s) in volume group “redhat” now active<\/strong>
      \n
      \n<\/strong><\/div>\n
      \n
      Creating SNAPSHOT (Backup):<\/div>\n

      We can take the back up of any particular Logical Volumes. Snapshot will be stored in the Same
      \nvolume group. Snapshot will take only 3-5% of the original size of Logical Volume.
      \nThis is the current status of our machine:<\/p>\n

      [root@vm4 ~]# lvs<\/div>\n
      LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/div>\n
      lvm1 linux -wi-a- 200.00M<\/div>\n
      lvm2 linux -wi-a- 40.00M<\/div>\n
      <\/div>\n
      [root@vm4 ~]# vgs<\/div>\n
      VG #PV #LV #SN Attr VSize VFree<\/div>\n
      linux 2 2 0 wz–n- 576.00M 336.00M<\/div>\n
      redhat 2 0 0 wz–n- 576.00M 576.00M<\/div>\n
      <\/div>\n
      [root@vm4 ~]# pvs<\/div>\n
      PV VG Fmt Attr PSize PFree<\/div>\n
      \/dev\/sda5 lvm2 — 290.21M 290.21M<\/div>\n
      \/dev\/sda6 linux lvm2 a- 288.00M 248.00M<\/div>\n
      \/dev\/sda7 linux lvm2 a- 288.00M 88.00M<\/div>\n
      \/dev\/sda8 redhat lvm2 a- 288.00M 288.00M<\/div>\n
      \/dev\/sda9 redhat lvm2 a- 288.00M 288.00M<\/div>\n
      <\/div>\n

      We have two Logical Volumes lvm1 and lvm2 mounted on \/linux1 and \/linux2 respectively.
      \nWe’ll take the SNAPSHOT of the LV lvm1 which is mounted on \/linux1
      \ncurrently there are following files in \/linux1 [ie in lvm1]
      \n[root@vm4 ~]# cd \/linux1<\/strong>
      \n[root@vm4 linux1]# ls<\/strong>
      \na b c lost+found<\/strong>
      \nStep1:<\/strong>
      \nSnapshot is actually a Logical Volume only. It will be saved in the same VG. We can create lvm
      \nsnapshot using command #lvcreate with options for snapshot.
      \nThe syntax is as follows<\/strong>
      \n#lvcreate –size SIZE –snapshot –name Name_Of_Snapshot Path_of_the_LV<\/strong>
      \n[root@vm4 linux1]# lvcreate –size 10M –snapshot –name snap \/dev\/linux\/lvm1<\/strong>
      \nRounding up size to full physical<\/strong><\/p>\n

      Logical volume “snap” created<\/strong>
      \n
      \n<\/strong>
      \n[root@vm4 linux1]# lvs<\/strong>
      \nLV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong>
      \nlvm1 linux owi-ao 200.00M<\/strong>
      \nlvm2 linux -wi-ao 40.00M<\/strong>
      \nsnap linux swi-a- 12.00M lvm1 0.10<\/strong>
      \n
      \n<\/strong>
      \n[root@vm4 linux1]# vgs<\/strong>
      \nVG #PV #LV #SN Attr VSize VFree<\/strong>
      \nlinux 2 3 1 wz–n- 576.00M 324.00M<\/strong>
      \nredhat 2 0 0 wz–n- 576.00M 576.00M<\/strong><\/p>\n<\/div>\n

      \n
      <\/div>\n

      Now lets mount the Snapshpot and check whether it has everything from lvm1.
      \nMounting snap to \/snapshot
      \n[root@vm4 linux1]# mkdir \/snapshot<\/strong>
      \n[root@vm4 linux1]# mount \/dev\/linux\/snap \/snapshot<\/strong>
      \n[root@vm4 linux1]# cd \/snapshot<\/strong>
      \n[root@vm4 snapshot]# ls<\/strong>
      \na b c lost+found<\/strong>
      \nIt has the same and all the contents of lvm1<\/p>\n

      How to create mirrored lvm volumes:
      \nWe can create mirrored lvm using the command #lvcreate with -m option.
      \nThe syntax is as follows:
      \n#lvcreate -L Size -m1 -n Name_LV Name_VG Mirror_1st_leg \u00a0 Mirror_2nd_leg \u00a0 Log_Device<\/strong>
      \n-m1 means its a mirrored one type. So it will have one original[1st leg] one mirror[2nd leg] and a
      \nlogging device for sync.
      \n#lvcreate -L 100M -m1 -n mlvm redhat \u00a0\/dev\/sda5 \u00a0\/dev\/sda6 \u00a0\/dev\/sda7<\/strong>
      \n[root@vm4 ~]# lvcreate -L 100M -m1 -n mlvm redhat \/dev\/sda5 \/dev\/sda6 \/dev\/sda7<\/strong>
      \n\/dev\/cdrom: open failed: Read-only file system
      \nLogical volume “mlvm” created
      \n[root@vm4 ~]# lvs<\/strong>
      \nLV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/strong>
      \nmlvm redhat mwi-a- 100.00M mlvm_mlog 100.00<\/strong>
      \n
      \n<\/strong><\/p>\n

      How to create stripped lvm volumes:
      \nWe can create lvms in stripped manner so that it will increase the performance. It can be done
      \nusing the commad #lvcreate with -i option.<\/p>\n

      The syntax is as follows:<\/div>\n
      #lvcreate -L Size -i2 -n Name_LV Name_VG 1st _LV 2nd _LV<\/div>\n
      [root@vm4 ~]# lvcreate -L 100M -i2 -n slvm redhat \/dev\/sda8 \/dev\/sda9<\/div>\n
      Using default stripesize 64.00 KB<\/div>\n
      \/dev\/cdrom: open failed: Read-only file system<\/div>\n
      Rounding size (25 extents) up to stripe boundary size (26 extents)<\/div>\n
      Logical volume “slvm” created<\/div>\n
      [root@vm4 ~]# lvs<\/div>\n
      LV VG Attr LSize Origin Snap% Move Log Copy% Convert<\/div>\n
      slvm redhat -wi-a- 104.00M<\/div>\n

      For extending a stripped lvm u need to extend the VG with two different PVs . Else it wont
      \nwork.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

      LVM in linux<\/p>\n

      Logical Volume Management[LVM]<\/p>\n

      LVM is a logical volume manager for the Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. The term “volume” refers to a disk drive or partition. Every system contains Physical Volums[PV]. Such as hard disks, partitions or external storages. Volume management treats PVs […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"_links":{"self":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/713"}],"collection":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=713"}],"version-history":[{"count":4,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/713\/revisions"}],"predecessor-version":[{"id":3079,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/713\/revisions\/3079"}],"wp:attachment":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=713"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=713"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=713"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}