This document shows how to add a 50GB hard disk on a CentOS 6 system, prepare it for usage with LVM, and mount it as the MySQL data directory. This was tested on a VMware Player virtual machine, with CentOS 6.4, and should be safe to run on any 6.x CentOS version.
Addition of new hard disk
The new disk was added on the CentOS 6.4 machine in VMware Player. The operating system doesn't see it yet, this is the previous status:
[root@c6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_c6-lv_root
18G 1.3G 16G 8% /
tmpfs 947M 0 947M 0% /dev/shm
/dev/sda1 194M 89M 96M 49% /boot
[root@c6 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_c6 lvm2 a-- 19.80g 0
[root@c6 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg_c6 1 2 0 wz--n- 19.80g 0
[root@c6 ~]# lvs
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv_root vg_c6 -wi-ao--- 17.80g
lv_swap vg_c6 -wi-ao--- 2.00g
fdisk sees the new /dev/sdb disk:
[root@c6 ~]# fdisk -l
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00072251
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 204800 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 26 2611 20765696 8e Linux LVM
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/vg_c6-lv_root: 19.1 GB, 19113443328 bytes
255 heads, 63 sectors/track, 2323 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/vg_c6-lv_swap: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Create a partition table
The first step to make this disk usable by the system, is to create a
partition table on it, with fdisk:
[root@c6 ~]# fdisk /dev/sdb
Print the current partition table with p. At the moment, there are no
partitions, so the output is empty:
Command (m for help): p
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1fdf1a3e
Device Boot Start End Blocks Id System
Create a new primary partition, with n, and allow it to occupy the
entire drive space:
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-6527, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-6527, default 6527):
Using default value 6527
Print the partition table again to verify:
Command (m for help): p
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1fdf1a3e
Device Boot Start End Blocks Id System
/dev/sdb1 1 6527 52428096 83 Linux
In the above output, the type of the partition is Linux, which is not
what we need. With t, set the type of the partition to 8e, i.e.
Linux LVM:
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Print the partition table once more, to verify:
Command (m for help): p
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1fdf1a3e
Device Boot Start End Blocks Id System
/dev/sdb1 1 6527 52428096 8e Linux LVM
That's more like it! Now save the new partition table with w:
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
Partial output of fdisk -l now shows that the partition is available
to the operating system for further handling:
[root@c6 ~]# fdisk -l
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1fdf1a3e
Device Boot Start End Blocks Id System
/dev/sdb1 1 6527 52428096 8e Linux LVM
Create LVM Physical Volume, Volume Group and Logical Volume
Next step is to create a new LVM Physical Volume:
[root@c6 ~]# pvcreate /dev/sdb1
Physical volume "/dev/sdb1" successfully created
The new PV now appears in pvs output:
[root@c6 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_c6 lvm2 a-- 19.80g 0
/dev/sdb1 lvm2 a-- 50.00g 50.00g
pvdisplay will now list the new physical volume, but it will be noted
as non-allocatable, in other words non usable yet, because it contains
no Volume Group:
[root@c6 ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_c6
PV Size 19.80 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 5069
Free PE 0
Allocated PE 5069
PV UUID LqOFBg-4lUi-Uen7-2vtO-EFkf-Cp8p-XvLiHX
"/dev/sdb1" is a new physical volume of "50.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb1
VG Name
PV Size 50.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID 6Nv0Xf-72ao-Nfph-TfvN-26FS-ssE8-QrEsXx
Create a new LVM Volume Group with vgcreate. In this example, the
Volume Group name is vg_mysql, because it's intended for use as the
data directory of a MySQL server, but it can be anything.
[root@c6 ~]# vgcreate vg_mysql /dev/sdb1
Volume group "vg_mysql" successfully created
The new VG will now show up in the output of vgs:
[root@c6 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg_c6 1 2 0 wz--n- 19.80g 0
vg_mysql 1 0 0 wz--n- 50.00g 50.00g
Now the output of pvdisplay will change, to show that the Physical
Volume is actually usable:
[root@c6 ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sdb1
VG Name vg_mysql
PV Size 50.00 GiB / not usable 3.31 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 12799
Free PE 12799
Allocated PE 0
PV UUID 6Nv0Xf-72ao-Nfph-TfvN-26FS-ssE8-QrEsXx
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_c6
PV Size 19.80 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 5069
Free PE 0
Allocated PE 5069
PV UUID LqOFBg-4lUi-Uen7-2vtO-EFkf-Cp8p-XvLiHX
Now that a Volume Group was created inside the Physical Volume, none of
the space on the Physical Volume is free any more, as shown in the
output of pvdisplay above, but all of the space in the Volume Group is
free, as shown by vgdisplay:
[root@c6 ~]# vgdisplay
--- Volume group ---
VG Name vg_mysql
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 50.00 GiB
PE Size 4.00 MiB
Total PE 12799
Alloc PE / Size 0 / 0
Free PE / Size 12799 / 50.00 GiB
VG UUID cwEyOs-rIqq-hc5J-cl45-kSZ0-i4dV-HiGE2l
--- Volume group ---
VG Name vg_c6
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size 19.80 GiB
PE Size 4.00 MiB
Total PE 5069
Alloc PE / Size 5069 / 19.80 GiB
Free PE / Size 0 / 0
VG UUID pp0134-mUkA-x3jp-FeVr-0ixo-Lxa4-eX1PCx
Next, create an LVM Logical Volume with lvcreate:
[root@c6 ~]# lvcreate -L 51196M -n lv_mysql vg_mysql
Logical volume "lv_mysql" created
In the above command, the size 51196M is the number of Physical Extends
(12799) multiplied by the size of the Physical Extend (4.0 MBytes). This
will cause the Logical Volume to occupy all of the Volume Group. Verify
with lvs:
[root@c6 ~]# lvs
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv_root vg_c6 -wi-ao--- 17.80g
lv_swap vg_c6 -wi-ao--- 2.00g
lv_mysql vg_mysql -wi-a---- 50.00g
Creating the filesystem
The next step is to create a filesystem inside the LVM Logical Volume.
The choice of filesystem depends on a multitude of factors, but for
this example let's stick with ext4:
[root@c6 ~]# mkfs.ext4 /dev/vg_mysql/lv_mysql
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
3276800 inodes, 13106176 blocks
655308 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
400 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
Mounting the filesystem
The last step in this procedure, is to actually mount the brand new filesystem at a mountpoint inside our filesystem hierarchy.
[root@c6 ~]# mkdir /mnt/test
[root@c6 ~]# mount /dev/vg_mysql/lv_mysql /mnt/test
[root@c6 ~]# mount | grep mysql
/dev/mapper/vg_mysql-lv_mysql on /mnt/test type ext4 (rw)
This verifies that our filesystem has been created, and can be mounted.
Setting up MySQL in the new Logical Volume
Very briefly, what you need to do to set up MySQL's data directory to be the new Logical Volume is:
Install, start, enable and automatically configure the MySQL Server:
[root@c6 ~]# yum -y install mysql-server [root@c6 ~]# service mysqld start [root@c6 ~]# chkconfig mysqld on [root@c6 ~]# mysql_secure_installationStop MySQL, back the original data directory up, mount the new one, and copy all the data over:
[root@c6 lib]# service mysqld stop [root@c6 lib]# cd /var/lib [root@c6 lib]# mv mysql mysql-original [root@c6 lib]# mkdir mysql [root@c6 lib]# mount /dev/vg_mysql/lv_mysql /var/lib/mysql [root@c6 lib]# chown mysql:mysql mysql [root@c6 lib]# cp -Rpv mysql-original/* mysql/ [root@c6 lib]# rm -rf mysql/lost+found/Finally, start the MySQL server again:
[root@c6 lib]# service mysqld start
That's it. You can now see that the new LVM Logical Volume is mounted, and is being used for MySQL:
[root@c6 lib]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_c6-lv_root
18G 17G 22M 100% /
tmpfs 947M 0 947M 0% /dev/shm
/dev/sda1 194M 89M 96M 48% /boot
/dev/mapper/vg_mysql-lv_mysql
50G 201M 47G 1% /var/lib/mysql