Task Description:

✨Elasticity Task Integrating LVM with Hadoop and providing Elasticity to Datanode Storage.

✨Increase or Decrease the Size of Static Partition in Linux.

Logical Volume Manager (LVM)

Traditional storage capacity is based on individual disk capacity. LVM uses a different concept. Storage space is managed by combining or pooling the capacity of the available drives. With traditional storage, three 1 TB disks are handled individually. With LVM, those same three disks are considered to be 3 TB of aggregated storage capacity. This is accomplished by designating the storage disks as Physical Volumes (PV), or storage capacity useable by LVM. The PVs are then added to one or more Volume Groups (VGs). The VGs are carved into one or more Logical Volumes (LVs), which then are treated as traditional partitions.

An administrator thinks of LVM as total combined storage space.

Three hard disk drives are combined into one volume group that is then carved into two logical volumes.

1. Install a new hard disk drive

There needs to be a storage disk available. Just physically install a drive in the server.

2. Designate Physical Volumes

Physical Volumes (PV) are disks or partitions that are available to LVM as potential storage capacity. We can mix and match drive types to create PVs. To implement LVM, first designate a drive as a Physical Volume.

For this first install LVM

Command to create a PV:

Display PV capacity and additional information:

Similarly creating another similar volume:

3. Manage Volume Groups

Once one or more of the disks are available to LVM as Physical Volumes, the storage capacity is combined into Volume Groups (VGs). There may be more than one VG on a server, and disks may be members of more than one VG (but PVs themselves may only be members of one VG).

Use the vgcreate command to create a new Volume Group. The VG must have at least one member.Use the following command to create a Volume Group named iiecvg with /dev/xvdf and /dev/xvdg as members:

Display information for a VG named iiecvg:

4. Manage Logical Volumes

he lvcreate command carves storage capacity from a VG. The syntax for the lvcreate command is as follows:

lvcreate -L size -n lvname vgname
Here is the command to create a 1 GB Logical Volume named mylv1 carved from the iiecvg Volume Group:

You can use the lvdisplay command to see the Logical Volume's configuration.

5. Apply a filesystem and set a mount point

Once the LV is created, it is managed as any other partition. It needs a filesystem and a mount point, just like we configured in the standard partition management section above.

1. Run the mkfs.ex4 command on the LV.
2. Create a mount point by using mkdir.
3. Manually mount the volume using the mount command.
4. Use the df -h command to verify the storage capacity is available.

Increase capacity

You can add storage capacity to the Logical Volume. This is useful if the users consume more space than you anticipated. The process is pretty logical:

1. Add a disk and configure it as a PV.
2. Add it to a VG.
3. Add the capacity to the LV and then extend the filesystem.

Reduce capacity

Reducing storage space is a less common task, but it’s worth noting. The process occurs in the opposite order from expanding storage.

Note: XFS filesystems are not actually shrunk. Instead, back up the content and then restore it to a newly-resized LV. You can use the xfsdump utility to accomplish this. The ext4 filesystem can be reduced.

First unmount it

umount /dev/iiecvg/mylv1

1. Shrink the filesystem

resize2fs /dev/iiecvg/mylv1 3k

2. Reduce the LV

Use the lvreduce command to shrink the storage space allocated to the LV. This returns the potential storage capacity to the VG.

 lvreduce -L 2T iiecvg/mylv1

Thank you