3.3 Creating an LVM Volume Group and Logical Volume

After you have installed MySQL, you are ready to set up the LVM volume group and logical volume where you will store a MySQL database. Sample values are used in the procedures in this section to help you understand what is required at each step. The overview provides only the Linux commands that you need to create and prepare the volume group for use by MySQL. The detailed description provides more information about the process, including the syntax and sample commands.

3.3.1 Sample Values

The procedures in this section uses the following parameters. Ensure that you replace the sample values with your values. The first node in the cluster is where you configure MySQL and the cluster resource.

Parameter

Sample Value

LVM physical volume

/dev/sdd

LVM volume group name

mysqlvg

LVM logical volume

msqllv

File system type

ext3

This is the file system type that you make on the LVM logical volume, such as ext2, ext3, reiserfs, or xfs.

Logical volume path

/dev/mysqlvg/mysqllv

Mount point for the logical volume

/mnt/mysql

Default MySQL root path

/var/lib/mysql

New MySQL root path

/mnt/mysql/var/lib/mysql

3.3.2 Setting Up the VG and LV (Overview)

You can create the volume group and logical volume by issuing the following LVM commands as the root user on the cluster node. This overview of the process uses the sample values. Ensure that you substitute your own values in the commands. For details, see Section 3.3.3, Setting up the VG and LV (Detailed).

Command Action

Command

1. Create the LVM physical volume.

pvcreate /dev/sdd

2. Create the clustered LVM volume group.

vgcreate -c y mysqlvg /dev/sdd

3. Activate the volume group exclusively on the node.

vgchange -a ey mysqlvg

4. Create the LVM logical volume.

lvcreate -n mysqllv -L size mysqlvg

5. Add a file system to the LVM logical volume.

mkfs -t ext3 /dev/mysqlvg/mysqllv [fs_options]

6. Create a mount point for the logical volume.

mkdir /mnt/mysql

You must also create this path on each node in the cluster.

7. Mount the LVM logical volume.

mount -t ext3 /dev/mysqlvg/mysqllv /mnt/mysql

8. Create the directory structure for the MySQL database files on the mounted logical volume.

cd /mnt/mysql
mkdir /mnt/mysql/var
mkdir /mnt/mysql/var/lib
mkdir /mnt/mysql/var/lib/mysql

9. Modify the file ownership of the mount point and subdirectories.

chown -R mysql:mysql /mnt/mysql

10. Deactivate the LVM logical volume.

vgchange -a n mysqlvg

3.3.3 Setting up the VG and LV (Detailed)

For detailed instructions, use the following procedure to create the LVM volume group and logical volume:

  1. Log in as the Linux root user to the first node of the cluster, then open a terminal console.

  2. In NSSMU, initialize the SAN device that you want to use for the MySQL database, but do not mark it as shareable for clustering:

    1. At the console prompt, launch NSSMU by entering:

      nssmu
      
    2. Select Devices, then press Enter.

    3. In the Devices list, select the unpartitioned device that you want to use, then press F3 to initialize it.

    4. Read the advisory, then press Y to confirm that you want to initialize the device.

    5. Specify the Master Boot Record (MBR) type as DOS or GPT, then press Enter.

      Typically, you use DOS format for devices up to 2 TB. You use GPT for devices greater than 2 TB.

    6. Verify that the device is initialized and that it is unshared (that is, Shareable for Clustering is set to No).

    7. Exit NSSMU to return to the command prompt.

  3. Create an LVM physical volume on the device (such as /dev/sdd) by entering:

    pvcreate <device>
    

    For example:

    pvcreate /dev/sdd
      No physical volume label read from /dev/sdd
      Physical volume "/dev/sdd" successfully created
    
  4. Create an LVM volume group (such as mysqlvg) on the physical volume by entering:

    vgcreate -c y <vg_name> <device>
    

    For example:

    vgcreate -c y "mysqlvg" /dev/sdd
      Clustered volume group "mysqlvg" successfully created
    

    The volume group is automatically activated.

  5. Activate the volume group exclusively on the current server by entering:

    vgchange -a ey <vg_name>
    

    The -a option activates the volume. The ey parameter specifies the values exclusively and yes.

    For example:

    vgchange -a ey mysqlvg
    
  6. View information about the volume group by using the vgdisplay command:

    vgdisplay <vg_name>
    

    Notice that 4 MB of the device are used for the volume group’s Physical Extent (PE) table. You must consider this reduction in available space on the volume group when you specify the size of the LVM logical volume in the next step (Step 7).

    For example:

    vgdisplay mysqlvg
      --- Volume group ---
      VG Name               mysqlvg
      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               508.00 MB
      PE Size               4.00 MB
      Total PE              127
      Alloc PE / Size       0 / 0   
      Free  PE / Size       127 / 508.00 MB
      VG UUID               rqyAd3-U2dg-HYLw-0SyN-loO7-jBH3-qHvySe
    
  7. Create an LVM logical volume (such as mysqllv) on the volume group by entering:

    lvcreate -n <lv_name> -L size <vg_name>
    

    Specify the logical volume name, size, and the name of the volume group where you want to create it. The size is specified in megabytes by default.

    The logical volume full path name is /dev/<vg_name>/<lv_name>.

    For example:

    lvcreate -n "mysqllv" -L 500 "mysqlvg"
      Logical volume "mysqllv" created
    

    This volume’s full path name is /dev/mysqlvg/mysqllv.

  8. View information about the logical volume by entering:

    lvdisplay -v <lv_path_name>
    

    For example:

    lvdisplay -v /dev/mysqlvg/mysqllv
        Using logical volume(s) on command line
      --- Logical volume ---
      LV Name                /dev/mysqlvg/mysqllv
      VG Name                mysqlvg
      LV UUID                nIfsMp-alRR-i4Lw-Wwdt-v5io-2hDN-qrWTLH
      LV Write Access        read/write
      LV Status              available
      # open                 0
      LV Size                500.00 MB
      Current LE             125
      Segments               1
      Allocation             inherit
      Read ahead sectors     auto
      - currently set to     1024
      Block device           253:1
    
  9. Create a file system (such as Ext2, Ext3, ReiserFS, or XFS) on the LVM logical volume by entering:

    mkfs -t <fs_type> <lv_path_name> [fs_options]
    

    You can specify file system options according to the type of file system you are making. For information, see the mkfs(8) man page and the related man page for the file system type, such as mkfs.ext2(8), mkfs.ext3(8), mkfs.reiserfs(8), or mkfs.xfs(8).

    For example:

    mkfs -t ext3 /dev/mysqlvg/mysqllv
      mke2fs 1.41.9 (22-Aug-2009)
      Filesystem label=
      OS type: Linux
      Block size=1024 (log=0)
      Fragment size=1024 (log=0)
      128016 inodes, 512000 blocks
      25600 blocks (5.00%) reserved for the super user
      First data block=1
      Maximum filesystem blocks=67633152
      63 block groups
      8192 blocks per group, 8192 fragments per group
      2032 inodes per group
      Superblock backups stored on blocks: 
        8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409
      Writing inode tables: done                            
      Creating journal (8192 blocks): done
      Writing superblocks and filesystem accounting information: done
    
      This filesystem will be automatically checked every 29 mounts or
        180 days, whichever comes first.  Use tune2fs -c or -i to override.
    
  10. Create a mount point for the logical volume by entering:

    mkdir /mnt/mysql
    
  11. Mount the logical volume on the MySQL mount point by entering:

    mount -t <fs_type> <lv_path_name> <mount_point>
    

    For example:

    mount -t ext3 /dev/mysqlvg/mysqllv /mnt/mysql
    
  12. Go to the mount point location (/mnt/mysql), then create the /var/lib/mysql subdirectory structure by entering:

    cd /mnt/mysql
    mkdir /mnt/mysql/var
    mkdir /mnt/mysql/var/lib
    mkdir /mnt/mysql/var/lib/mysql
    
  13. Change the owner and group owner of the /mnt/mysql directory and its contents to use the mysql user and group. Enter the chown command with the recursive (-R) option:

    cd /mnt
    chown -R mysql:mysql mysql
    

    Another way to do this is to explicitly specify the directory path:

    chown -R mysql:mysql /mnt/mysql
    
  14. Continue with Section 3.4, Configuring MySQL on the LVM Logical Volume.