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So friends, let's talk about another story solution, this one known as LVM, Log

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ical Volume

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Management. This happens to be one of my favourite technologies in all of Linux

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, so let's just dive

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in. So, you know the problem with storage, everyone wants more storage no

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matter how much you buy,

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eventually you always seem to run out. So the question is, is that when we

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happen to run out,

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how do we address that particular problem? Well, very often what you might do

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is just go and,

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you know, buy more storage that might be an external hard drive, maybe it's a
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you know, buy more storage that might be an external hard drive, maybe it's a

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USB pin,

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whatever it may be. Who knows, maybe you need a ton of storage and you go and

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buy a massive server.

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Now all of these are certainly viable options, they definitely do work, they

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will solve your problem,

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but is it the most efficient way to go about solving that particular problem?

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Let me give you a

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simple example, let's maybe say in your home you happen to have a spare drive

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that happens to have

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50 gigabytes on it. Now for whatever reason, you maybe need an additional 100
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50 gigabytes on it. Now for whatever reason, you maybe need an additional 100

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gig of storage,

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so as it stands right now, this particular storage device is not going to be

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good enough

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to handle the request or the requirement should I say of the 100 gig. So the

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temptation might be to

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think that the 50 gigabyte one is useless and what you might have to do is to

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go and buy a brand

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new fresh 100 gig bit of storage via an external hard drive via a USB whatever

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it may be. Now what

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if I told you that even though the 50 gig by itself is not sufficient to cover
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if I told you that even though the 50 gig by itself is not sufficient to cover

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all your storage

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needs, but it can be used in conjunction to support that particular solution

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that you're looking for?

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Well, I'm actually hinting at the use of LVM because that is going to allow us

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to make use of

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disparate physical storage devices and effectively aggregate them and it is

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this type of aggregation

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that is going to allow us to make use of in the example we just saw the 50 gig

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abyte storage device

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that would ultimately be rather useless. So you're now here that you can make
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that would ultimately be rather useless. So you're now here that you can make

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use of these old

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storage devices. You go rummaging through your house and you find even more old

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storage devices.

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So like I say you have your 50 gig storage device, maybe you find three more 10

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gigabyte

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ones. So in reality what we actually have here is a total of 80 gig of storage

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space that is not

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being used. So as opposed to having to go out and buy one contiguous block of

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100 gig storage space,

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what if we just jump out and buy a fairly cheap 20 gig storage device?
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what if we just jump out and buy a fairly cheap 20 gig storage device?

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Certainly more

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but cheaper than the 100 gig and all we will do is we will use this new

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purchase in conjunction

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with remaining 80 gig storage that we just found laying about the house. So

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like I have hinted

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that this is all going to be enabled via logical volume management but we have

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to understand the

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constituent concepts that make up the LVM architecture. Now the first concept

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we have to

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understand is something known as a PV otherwise known as a physical volume. Now
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understand is something known as a PV otherwise known as a physical volume. Now

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the PV's are the

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actual physical discs that we're going to use for storage. So in my case here

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my 50 gig storage

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device would become an LVM physical volume. Same with the 310 gig and the newly

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purchased 20 gig

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storage device they would all be my physical volumes. That's the first concept

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in the architecture.

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The next concept is the VG. This is known as the volume group. Now the volume

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group is quite

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simply the aggregation of those physical volumes. So realistically the volume
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simply the aggregation of those physical volumes. So realistically the volume

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group is going to be

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the combined result of the physical volumes grouped together. It's going to

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give us one big logical

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blob of storage. So imagine it like this. Here is our 50 gig storage device,

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here is our 20 gig

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storage device and then we have our 310 gig storage devices. Individually they

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are all physical volumes

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but via the technology of LVM logically what they become is this big contiguous

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chunk of storage
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chunk of storage

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at 100 gig. That would be the volume group. Now that is just two components of

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the architecture.

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We have one more component we have to understand and that is how we are going

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to effectively subdivide

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this volume group because just because we have aggregated these physical discs.

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And to one big blob doesn't mean we have to use it as one big blob we can

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logically subdivide

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this into many smaller chunks. We could effectively chop it up into equal sizes

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if we so wish.

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Let's say we wanted to quarter it. Then we could have four equally sized
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Let's say we wanted to quarter it. Then we could have four equally sized

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partitions made up of all

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of these asymmetric physical volumes. A 50 and a 20 and a 10 10 10 suddenly

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been able to be subdivided

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into 425 gig partitions. These particular partitions carved out of the volume

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group would be the

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logical volumes. Now one thing to note is that we don't actually have to subdiv

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ide these in a

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symmetric manner. What we could do is I could maybe create one partition space

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of 75 gig and then
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of 75 gig and then

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for the remaining 25 gig I could create another partition which is only 10 in

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size and another

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which is 15 in size. Now we effectively have three partitions of varying size

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of carved out from

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the 100 gigabyte volume group. This is the type of flexibility that we get with

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LVM.

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So with that primer out the way let's dive in and begin it seeing how we can

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automate this

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particular process. So if you search for the Ansible LVM module if we click

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this link right here once
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this link right here once

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again this is going to be part of the Ansible Community General module

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collection. And notice

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here what this particular module does it allows you to create remove or resize

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volume groups that

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has our VGs. So once again you can go through all of the particular parameters

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to see how we can

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actually use this particular option. Notice we have this PVS option here. And

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this allows us to

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specify which physical volumes i.e. which actual disks should be combined to

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make the volume group.

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And this is going to be accepted in the form of a list comprising of strings.
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And this is going to be accepted in the form of a list comprising of strings.

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Notice the very

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important option here specifying VG. This is a require parameter and this is

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going to be the name

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of the volume group. So here is what I'm going to do. I'm first going to shut

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down my blue box

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right now. I'm going to add in some new devices once again. So I'll go to my

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options here. Click

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settings. I'm going to go to hard disk and then I will choose add a device and

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I'll choose a new

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hard disk and then select add. I'm going to give this one a size of let's maybe
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hard disk and then select add. I'm going to give this one a size of let's maybe

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say 3GB and I will

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choose apply. If I go back to show all I can choose hard disk again. Select add

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a device. Choose

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another new hard disk. Add it. And let's just maybe make this one 4GB so it's a

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little bit different

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okay. So let's apply this to kill. So if I parallel this back on again give it

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a moment to boot up.

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So now if I log into this device. So if I just say so though parted dash L and

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type in the password

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for the user. As we can see we have dev NVMe 0n3. We have the actual size right

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here. And if I

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just scroll on up a little bit further we can actually see NVMe 0n4 which has a
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just scroll on up a little bit further we can actually see NVMe 0n4 which has a

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different storage

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capacity. These are the two physical disks that I'm going to combine to make a

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volume group.

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So let's go back to my control machine here. So let's create a playbook called

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play3.yml.

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Going to insert mode have a three hyphens at the top give the playbook in name

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as per usual.

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I should call this play3lvmstuff. And all I'm going to do is I'll target the

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blue box in this case

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here but not actually added the devices for the yellow box. And in the case
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here but not actually added the devices for the yellow box. And in the case

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here I will just say

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gather facts as false to keep things nice and fast. And now I'll begin defining

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my task of the first

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task. It's going to be create a vg. Now what we're going to use we're going to

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use the community.general.lvg

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module. And we're going to have to specify a few things. The first thing is I'm

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going to say that

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the state should be present. We have to specify the volume group name. I'll

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just call this nugget

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storage. And now I'll specify my physical volumes that are going to comprise of

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the script. Now

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remember it's going to be in the form of a list object. So here's my hyphen.
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remember it's going to be in the form of a list object. So here's my hyphen.

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And the first disk

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is going to be dev nvm3. And the second one is going to be dev nvm4. So with

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that now done we

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should be able to create a volume group. So I will say answerable play3.yml and

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to enter.

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Oh and I have a typo right here. Let me go in. That should be nvm3. But silly

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there. Try that

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entirely again. Switch these around. Write the changes. Arrow up and try again.
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entirely again. Switch these around. Write the changes. Arrow up and try again.

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And this looks

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a lot healthier. We have a change. So let's go here. Go back to the blue box.

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If I just say

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pseudo VGS, we can actually see the volume group that we have created. Check

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this out. Nugget

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storage. And we can see here the size is seven gig because we have one device

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that comprises of

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three gig storage. And another which comprises of four four and three gives us

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that logical

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grouping of seven gig storage space. Now right now we have a volume group. If

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you want to subdivide
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you want to subdivide

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that into our logical volumes, we have another module to do so. So if you

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search for answerable

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elvall, this particular module here once again from the same collection, this

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is going to allow

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us to create remove or resize logical volumes. So once again, we can go through

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all of the

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particular options, we can specify the name of the logical volume. We have

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options to resize

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file systems, that type of thing. We can specify should the state be present or

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absence. And notice

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very crucially, we have this required parameter of VG, which is going to take a
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very crucially, we have this required parameter of VG, which is going to take a

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string. Pretty much

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which volume group do we want to be carving up. Now one last thing, which is

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obviously important

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is the size of the logical volume. So we have our size parameter. And if we

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scroll on down,

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we can see some examples. So notice we can specify the size and units, i.e. we

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can specify megabytes

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in this case here, or the example below we can specify gigabytes. Or if we

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switch, we can specify

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the size as a percentage. One thing to note though, is if we happen to utilize

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a percentage as the

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size, the module is not going to act in an idempotent manner. So just be aware
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size, the module is not going to act in an idempotent manner. So just be aware

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of that if you choose

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to use that particular option. So let's go and see how this actually looks then

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. So what I will do

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is I'll go into my play three dot yml. And I'm going to have another task here.

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So let's give this a

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name. And I'll just say create first logical volume, the module will be

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community general, elvall,

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I'll specify that the VG I'm going to be targeting is going to be the nugget

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storage volume group.

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And I'll specify the name of this logical volume is going to be, let's just

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call it my first chunk.
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call it my first chunk.

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Now specify the size of this logical volume. And let's say I want to create 512

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meg. So if I just

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happen to save this right here, and I run the playbook and to enter give it a

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moment. As we can

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see here, the volume group was already created, but we do have a change with

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respect to the logical

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volume. Let's go and inspect it. So we have our device, if I notice a pseudo V

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GS type in my password.

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Notice before the free space was pretty much seven gig. And now the free space

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is now 6.5 gig.
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is now 6.5 gig.

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That's because if I now type the command pseudo LVS, we can actually see here I

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have created a

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logical volume called my first chunk carved out of the nugget storage volume

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group of the size 512

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meg. And if I wanted to create another chunk, what I could do is go back into

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the playbook.

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Let's give us a name. We'll just create second LV, use the same module specify

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we want to carve

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the next logical volume out of the same volume group. That is the nugget

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storage. I specify this

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logical volume here can be called, let's say my second bigger chunk. Okay. And
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logical volume here can be called, let's say my second bigger chunk. Okay. And

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this time the size

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is going to be what do we have left? We've got 6.5 left. Let's maybe go for a

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second volume of

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4G. Okay. So let's save this and run the playbook. Notice we have item potency

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on the first volume

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that was just skipped. But the creation of the second volume that actually

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invoked a change on

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the device. So let's go back. Now if I say pseudo VGS, the free space is now

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down to 2.5 gig. And if I
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down to 2.5 gig. And if I

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do pseudo LVS, notice we have a second logical volume once again carved out

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from the same storage

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chunk this time for gig and size.