Adding Disk Space to a Logical Volume Manager

In many scenarios, the default disk allocation for Linux partitions is inadequate for installation of larger HANA-based systems. This guide will detail formatting additional disk volumes and extending the Linux Volume Manager (LVM) partitions to include the added space.

In my scenario, I found it necessary to extend both /var and /opt directories when installing Hadoop, which I will walk through below.

Steps:

1. Creating the Volume
2. Adding the volume to volume group
3. Extending the volume partitions

Creating the Volume

This step will be specific to your environment. In cloud scenarios additional virtual disks can often be attached to nodes in your cluster, or actual physical disks can be added to each node. Once added, the disk should be accessible from /dev/sd*. The exact letter will depend on the number of disks attached (/dev/sda, /dev/sdb, /dev/sdc, etc.)

Adding the volume to volume group

Next we need to SSH to the instance where we attached the volume. Once connected log in as root.

In my case, my disk is available at /dev/sdb by default

# ls -al /dev/xxxx/vol-e338e620

lrwxrwxrwx 1 root root 6 Feb 14 20:13 /dev/xxxx/vol-e338e620-> ../sdb

Right now, our connected hard drive is on /dev/sda and is split into two paritions: a boot partition (sda1) and the LVM hard drive partition (sda2). Our attached storage (sdb) is still un-formatted and without a filesystem:

# fdisk -l /dev/sda

Disk /dev/sda: 64.4 GB, 64424509440 bytes
255 heads, 63 sectors/track, 7832 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: 0x0009dda3

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          39      307200   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              39        7833    62606336   8e  Linux LVM


# fdisk -l /dev/sdb

Disk /dev/sdb: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 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

We need to identify the volume group (VG) being used as this is what we will need to extend. You can confirm the name of the VG using vgdisplay like below:

# vgdisplay

  --- Volume group ---
  VG Name               VOL
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  7
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                6
  Open LV               6
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               59.69 GiB
  PE Size               32.00 MiB
  Total PE              1910
  Alloc PE / Size       1910 / 59.69 GiB
  Free  PE / Size       0 / 0
  VG UUID               YthGca-Su6c-LgkQ-5Miy-XIOI-heyb-da4nuO

We’ll use fdisk to create a new partition of type 8e (Linux LVM). The order of commands is below:

# fdisk /dev/sdb

n - create a new partition
p - specify primary
[enter] x2 - use the entire disk
t - change type
8e - Linux LVM type
w - write partition table to disk and exit

Within fdisk, press m at any point to see a list of possible commands. Once written, your new disk should look like this:

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       32635   262140606   8e  Linux LVM

Now we create a new Physical Volume (PV) to use this new partition using pvcreate command:

# pvcreate /dev/sdb1

Physical volume "/dev/sdb1" successfully created

Next, use pvextend to extend our volume group VOL to include the new volume:

# vgextend /dev/VOL /dev/sdb1

Volume group "VOL" successfully extended

Extending the volume partitions

Finally we’ll extend our partitions and then resize the filesystem. You can see a list of all partitions under /dev/VOL/.

First, we’ll use lvextend to extend each logical volume. In this example I am assigning an additional 100GB to each node:

# lvextend -L +100G /dev/VOL/opt

Size of logical volume VOL/opt changed from 7.72 GiB (247 extents) to 107.72 GiB (3447 extents).
  Logical volume opt successfully resized


# lvextend -L +100G /dev/VOL/var

Size of logical volume VOL/var changed from 5.94 GiB (190 extents) to 105.94 GiB (3390 extents).
  Logical volume var successfully resized.

Now in order to use the new space, we need to extend the filesystem. The command run will depend on the filesystem in use. Issuing df -T will provide the filesystems for all disks. For ext2, ext3, and ext4 filesystems we can use resize2fs:

# resize2fs /dev/VOL/var

resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VOL/var is mounted on /var; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 7
Performing an on-line resize of /dev/VOL/var to 27770880 (4k) blocks.
The filesystem on /dev/VOL/var is now 27770880 blocks long.


# resize2fs /dev/VOL/opt

resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VOL/opt is mounted on /opt; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 7
Performing an on-line resize of /dev/VOL/opt to 28237824 (4k) blocks.
The filesystem on /dev/VOL/opt is now 28237824 blocks long.

Your volumes should now be extended! You can confirm by issuing df -h. Below, we can see /var is now 105G and /opt is 106G:

# df -h

Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VOL-root   32G  2.3G   28G   8% /
tmpfs                  16G     0   16G   0% /dev/shm
/dev/sda1             283M   32M  236M  12% /boot
/dev/mapper/VOL-home  2.9G  4.6M  2.8G   1% /home
/dev/mapper/VOL-opt   106G  4.8G   96G   5% /opt
/dev/mapper/VOL-tmp   7.5G   48M  7.1G   1% /tmp
/dev/mapper/VOL-var   105G  2.5G   97G   3% /var