Demand scenario

"Merge" the two 18T data disk spaces of the MySQL host and mount them to / MySQL_ In the data directory, the file system is required to be formatted as xfs; The existing key information is summarized as follows:

• Data disk to be mounted
  • /dev/sdb: 18T
  • /dev/sdc: 18T
• File system: xfs
• Mount Directory: / mysql_data

Operating system environment

• OS version: CentOS 7.5
• LVM version: lvm2

Implementation method

To achieve this requirement, LVM logical volume management can be used.

Implementation steps

Disk partition -- this step is not required

Before using a disk or disk partition as a physical volume (PV), you need to initialize it, that is, partition the disk; Because the disk partition requirement is greater than 2T, fdisk cannot be managed. You need to use the parted command for disk partition management; For detailed usage of parted, please refer to previous blogs of bloggers: Use the parted command to partition the disk

• /dev/sdb

# The new disk label type of / dev/sdb is GPT
[root@MYSQL-SERVER ~]# parted /dev/sdb mklabel gpt 
# Allocate the entire space of / dev/sdb to the same partition
[root@MYSQL-SERVER ~]# parted /dev/sdb mkpart primary 0 100%
Warning: The resulting partition is not properly aligned for best performance.
Ignore/Cancel? I                                                          
Information: You may need to update /etc/fstab.

• /dev/sdc

# The new disk label type of / dev/sdc is GPT
[root@MYSQL-SERVER ~]# parted /dev/sdc mklabel gpt 
# Allocate the entire space of / dev/sdc to the same partition
[root@MYSQL-SERVER ~]# parted /dev/sdc mkpart primary 0 100%
Warning: The resulting partition is not properly aligned for best performance.
Ignore/Cancel? I                                                          
Information: You may need to update /etc/fstab.

Create physical volume

The command to create a physical volume is pvcreate; Use this command to create all partitions or disks that you want to add to the volume group as physical volumes;
Create partitions / dev/sdb1 and / dev/sdc1 as physical volumes:

[root@MYSQL-SERVER ~]#  pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created.
[root@MYSQL-SERVER ~]#  pvcreate /dev/sdc1
  Physical volume "/dev/sdc1" successfully created.

Create volume group

The command to create a volume group is vgcreate; Use this command to create the physical volume created by pvcreate as a complete volume group;
Create the physical volume / dev/sdb1 as a volume group named vgmysql:

[root@MYSQL-SERVER ~]#  vgcreate vgmysql /dev/sdb1
  Volume group "vgmysql" successfully created

Add a new physical volume to the volume group

This step is the key step to combine the two disk spaces into one; When a new disk or a new physical volume is added to the system and you want to add it to an existing volume group, you can use the vgextend command;
Add the physical volume / dev/sdc1 to the vgmysql volume group:

[root@MYSQL-SERVER ~]#  vgextend vgmysql /dev/sdc1
  Volume group "vgmysql" successfully extended

Viewing volume groups

View vgs for volume groups:

[root@MYSQL-SERVER ~]#  vgs
  VG      #PV #LV #SN Attr   VSize   VFree 
  vgmysql   2   0   0 wz--n-  32.74t 32.74t
  vgroot    1   4   0 wz--n- 264.00g  4.00m

From the echo result of the vgs command, the volume group vgmysql is successfully added, and its total space is the total size of the two physical disks (not the exact 38T due to different conversion units).

Create logical volume

The command to create a logical volume is lvcreate; Use this command to create a logical volume on the volume group established with vgcreate;
Create a logical volume named lvmysql on the volume group vgmysql, with a starting size of 32.7T;

• -n: Specifies the logical volume name
• -50: Specifies the logical volume size

[root@MYSQL-SERVER ~]#  lvcreate -L 32.7T -n lvmysql vgmysql 
  Rounding up size to full physical extent 32.70 TiB
  Logical volume "lvmysql" created.

Format logical volumes

Format the created lvmysql logical volume as xfs

[root@MYSQL-SERVER ~]#  mkfs -t xfs /dev/vgmysql/lvmysql
meta-data=/dev/vgmysql/lvmysql   isize=512    agcount=33, agsize=268435328 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=0, rmapbt=0, reflink=0
data     =                       bsize=4096   blocks=8777839616, imaxpct=5
         =                       sunit=64     swidth=64 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=521728, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

Create a mount directory and mount

• Create mount directory / mysql_data

[root@MYSQL-SERVER ~]#  mkdir /mysql_data

• mount

[root@MYSQL-SERVER ~]#  mount /dev/vgmysql/lvmysql /mysql_data/

• Do boot auto mount

echo '
/dev/mapper/vgmysql-lvmysql /mysql_data xfs     defaults 0 0' >/etc/fstab

Check whether the mount is successful

[root@MYSQL-SERVER ~]#  df -h
Filesystem                   Size  Used Avail Use% Mounted on
/dev/mapper/vgroot-lv_root    40G  1.8G   36G   5% /
devtmpfs                     126G     0  126G   0% /dev
tmpfs                        126G     0  126G   0% /dev/shm
tmpfs                        126G  1.1M  126G   1% /run
tmpfs                        126G     0  126G   0% /sys/fs/cgroup
/dev/sda1                    976M  197M  713M  22% /boot
/dev/mapper/vgroot-lv_var     59G  197M   56G   1% /var
/dev/mapper/vgroot-lv_home    99G  5.6G   88G   6% /home
tmpfs                         26G     0   26G   0% /run/user/0
/dev/mapper/vgmysql-lvmysql   33T   34M   33T   1% /mysql_data
[root@MYSQL-SERVER ~]#  lsblk 
NAME                MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                   8:0    0 446.1G  0 disk 
├─sda1                8:1    0     1G  0 part /boot
├─sda2                8:2    0   264G  0 part 
│ ├─vgroot-lv_root  253:0    0    40G  0 lvm  /
│ ├─vgroot-lv_swap  253:1    0    64G  0 lvm  [SWAP]
│ ├─vgroot-lv_var   253:2    0    60G  0 lvm  /var
│ └─vgroot-lv_home  253:3    0   100G  0 lvm  /home
└─sda3                8:3    0    64M  0 part 
sdb                   8:16   0  16.4T  0 disk 
└─sdb1                8:17   0  16.4T  0 part 
  └─vgmysql-lvmysql 253:4    0  32.7T  0 lvm  /mysql_data
sdc                   8:32   0  16.4T  0 disk 
└─sdc1                8:33   0  16.4T  0 part 
  └─vgmysql-lvmysql 253:4    0  32.7T  0 lvm  /mysql_data
nvme0n1             259:0    0   1.5T  0 disk 
[root@MYSQL-SERVER ~]#  blkid 
/dev/sda1: UUID="5a350fc9-d3d2-44c7-9574-30bf9a9dd0d3" TYPE="ext4" 
/dev/sda2: UUID="Sum0Mm-6ShR-6ajh-cYQO-091c-r7QI-zfbDpm" TYPE="LVM2_member" 
/dev/sda3: UUID="2019-05-24-11-39-22-00" LABEL="config-2" TYPE="iso9660" 
/dev/mapper/vgroot-lv_root: UUID="df07731a-5e56-4cc3-95ab-b723b5979332" TYPE="ext4" 
/dev/mapper/vgroot-lv_swap: UUID="7b5cd64d-d316-430d-8a83-aca89c4708d2" TYPE="swap" 
/dev/mapper/vgroot-lv_var: UUID="025cb128-de8f-4bca-8206-5c1601e79715" TYPE="ext4" 
/dev/mapper/vgroot-lv_home: UUID="7bd155b6-9200-442a-a61a-32076c0e4b7e" TYPE="ext4"