A volume group (
VG) is the central unit of the Logical Volume Manager (LVM) architecture. It is what we create when we combine multiple physical volumes to create a single storage structure, equal to the storage capacity of the combined physical devices. Physical volumes are devices that are initialized using LVM, i.e., hard disk drives, solid-state drives, partitions, etc.
When we take two 1Gb physical volumes and create a volume group, we end up with a consolidated storage capacity of 2Gb. Now that we have a basic understanding of what a volume group is, let's take a look at how to create and configure these in Linux. I will be using Red Hat Enterprise Linux 8 for the following examples.
[root@rhel ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 rhel lvm2 a-- <29.00g 0 /dev/sdb lvm2 --- 1.00g 1.00g /dev/sdc lvm2 --- 1.00g 1.00g>
You will notice that
/dev/sdc are initialized as physical volumes but do not belong to a Volume Group (whereas
/dev/sda2 belongs to the volume group
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Ok, now that we have nailed down the "what and why," let's configure a volume group using the two physical volumes illustrated above. You can see the creation and initialization of these groups in my article, How to create physical volumes in Linux using LVM.
We are going to combine
/dev/sdc into a volume group. First, we will need to name the group. For test purposes, I will call our group
LVMvgTEST. Now that we have decided on a name, let's use a single command to add both physical volumes to the new volume group. This command needs to be run as
root or with
[root@rhel ~]# vgcreate LVMvgTEST /dev/sdb /dev/sdc Volume group "LVMvgTEST" successfully created
You can see in the output that the volume group was successfully created. Now we can use the
pvs command to see the change to our storage architecture.
[root@rhel ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 rhel lvm2 a-- <29.00g 0 /dev/sdb LVMvgTEST lvm2 a-- 1020.00m 1020.00m /dev/sdc LVMvgTEST lvm2 a-- 1020.00m 1020.00m
Now you can see that
/dev/sbc are a part of our
LVMvgTEST volume group.
Congratulations on the volume group creation! If you're thinking, "Well, what now?" I recommend that you continue exploring LVM and use
lvcreate to create logical volumes. There are many ways to do this, so do your research! I will cover these in a future article, so keep an eye out for that!
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