Chapter 15 - Managing Advanced Storage

Question 1

What is an important advantage of LVM (Logical Volume Manager)?

Answer 1

LVM offers a flexible solution for managing storage. Volumes are no longer bound to the restrictions of physical hard drives. If additional storage space is needed, the volume group can easily be extended by adding a new physical volume, so that disk
space can be added to the logical volumes.

Question 2

What is another advantage of LVM besides flexible storage management?

Answer 2

1. LVM supports snapshots
2. If a hard disk is failing, data can be moved within the volume group (through the pvmove command), the failing disk can then be removed from the volume group, and a new hard disk can be added dynamically.

Question 3

What is a snapshot in LVM?

Answer 3

A snapshot is a copy of the current state of the logical volume.

Question 4

How is a snapshot in LVM created?

Answer 4

LVM snapshots are created by copying the logical volume administrative data (the metadata) that describes the current state of files to a snapshot volume.

Question 5

What command is used to mode data between volume groups?

Answer 5

pvmove command

Question 6

Which command to create logical volumes?

Answer 6

pvcreate

Question 7

In the fdisk an gdisk utilities what is the option to use to change the partition type from the menu?

Answer 7

“t” option

Question 8

What is the partition type code for a LVM partition in fdisk and gdisk?

Answer 8

in fdisk it is 8e

in gdisk it is 8e00

Question 9

Which command to use to flag a LVM partition to be used as a physical volume?

Answer 9

pvcreate

Question 10

Which command to use to verify if the physical volume has been created?

Answer 10

pvs

Question 11

Which command to use to see a summary of the physical

volumes and their attributes?

Answer 11

pvs or pvdisplay

Question 12

Which command to get a very compact overview of the current storage configuration on your server?

Answer 12

lsblk

Question 13

How to use the vgcreate command?

Answer 13

Type vgcreate followed by the name of the volume group you want to create and the name of the physical device you want to add to it.
Eg. vgcreate vgdata /dev/sdc1

Question 14

What is a physical extent size in volume groups?

Answer 14

The physical extent size defines the size of the building blocks used to create logical volumes. A logical
volume always has a size that is a multiple of the physical extent size

Question 15

What command to use to specify the physical extent size you want to use?

Answer 15

vgcreate -s

Question 16

What command to request details about the volume group?

Answer 16

vgs or vgdisplay?

Question 17

What is a device mapper?

Answer 17

Device mapper or dm is a generic interface that the Linux kernel uses to address storage devices.

Question 18

What is a disadvantage of using XFS filesystem?

Answer 18

If the XFS file system is used, a volume can be increased, but not decreased, in size.

Question 19

Which volume group command is used to extend a volume group or reduce a volume group?

Answer 19

vgextend and vgreduce

Question 20

What is VDO?

Answer 20

Virtual Data Optimizer

Question 21

What are the differnent scenarios where VDO can be useful?

Answer 21

host platforms for container
host platforms for virtual machines
cloud backup storage