Hello World,

I’ve recently received the question about a how to resize the virtual disk of a virtual machine.  In this previous post, we already talked about this topic.  At that time, we discussed on how to resize disks when the vm files were located on local storage.   In this post, we will see how you can resize virtual disks of your virtual machines if the VM files are located on a LVM group.  

LVM Groups in Proxmox VE

Based on the proxmox ve wiki pages about storage model used by Proxmox VE, we know that the preferred storage model is to use LVM Groups.   When working with LVM Groups, you can use 2 different configuration.  You can use local storage to create your LVM Groups (aka LVM groups with Local backing).  If you have an iscsi infrastructure, you can use the network storage infrastructure to build up your LVM groups as well. This configuration is often called LVM Group with Network backing.  

In this post, we will quickly demonstrate how to create these LVM Groups with network backing.  Based on this configuration in our Proxmox VE infrastructure, we should be able to demonstrate how to achieve in an elegant way the resizing of a virtual disk.  Let’s start….

Creating your LVM Groups with Network Backing

We assume that you have already an up and running iscsi infrastructure ready to be used by the Proxmox VE infrastructure.  We assume that a iscsi target is already available and that we just need to connect to it from our Proxmox VE infrastructure.

Step 1 – Connect to the iSCSI Target

When you are ready with your iscsi infrastructure, you can open the Proxmox VE web interface and click on the Datacenter node in the Tree.  In the right pane, you will see the Storage Tab.  In this page, you will see the “Add” button at top left.  Click on it and you will see a dropdown menu.  From the menu, select the ISCSI target.

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You will see a small dialog box form similar to the following screenshot

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You will need to enter the required information.

• in the ID field, provide a name that will help you identify the iSCSI target you are about to connect to
• In the Portal field, provide the ip address of the iscsi appliance/server that will be serving the iscsi disks
• In the target field, you will see the availabe iscsi target that you can connect to.  Select the appropriate one
• Ensure that you uncheck the box “Use LUNs direclty”.  The checkbox is enabled by default

Press Add when you are ready.  Within the Web Interface, you should see an additional storage item displayed.

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Step 2 – Create your LVM Group on top of the iscsi target

Again, from the storage tab, you will click on Add.  From the drop down menu, you will select the option LVM Group.

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The following input box will be displayed.

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Again, you will have to provide the correct information.

• In the ID field, provide a name that can help you identify this LVM Group.
• In the base storage, from the dropdown box, select the iscsi target you’ve just created in the previous step

 

After selecting the base storage, you will see  2 additionial fields displayed in the dialog box.

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• Select the base volume to be used
• Provide a name for the volume group
• ensure that you’ve ticked both checkboxes in this wizard.

At the end of the process, within the web interface, you should see that the LVM storage object has been created.

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Creating your Virtual Machine and store it on the LVM group

Here, we will simply create a virtual machine that will be located on the LVM Group we have just created in the previous step.  We will create a virtual machine with a small disk. In the following steps, we will increase the size of the disk.

To create your virtual machine, from within the Web server, you click on the Create VM button in the top right corner of the interface.  The Create VM Wizard will start.

In the general tab, Provide the requested information. Press Next

 

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In the Hard disk page, in the storage field drop down menu, ensure that you select the LVM Group.  Specify the size of the hard disk.  Accept default configuration

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Accept default configuration in the rest of the Wizard.  In the confirm tab, click confirm and the virual machine will be created for you.  You can review the configuration of the virtual machine within the web interface (see screenshot)

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We have installed Windows 2003 as operating system on the newly created virtual machine.  The following screenshot shows that the virtual machine is using a 12-GB hard disk.  We will need to increase the size

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Resizing the disk of the Virtual Machine

That’s the part that you are probably interested in.  As you will see the process is quite simple.  Most of the operation are to be performed from the command line. So, connect to your proxmox console.

Step 1 – Shut down the virtual machine

As a best practice, ensure that the virtual machine is turned Off before resizing the disk.

Step 2 – Get information about your LVM Groups by issuing the following command

• lvdisplay 

From the output, you have to find out on which LV your virtual machine is located. In my example, the virtual machine that needs to be reconfigured is stored on the LV Name /dev/Legacy/vm-103-disk-1.  (see screenshot above).   Write down the LV Name because you will need it later. Note also the size of the disk : 12 GB

Step 3 – resizing the disk of the virtual machine

Using the lvresize command, you will be able to increase/decrease the size of the hard disk.  If you type lvresize –help, you will get an idea on how to use it

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Let’s assume that in our example, we need to increase the size of hard disk by 1 GB, you will then type the following command

• lvresize -L+xGB   <LV NAME>

• lvresize -L+1GB /dev/Legacy/vm-103-disk-1

Step 4 – Update the information about the size

If you issue again the command lvdisplay,  you should see that the size of the disk has increased passing from 12 GB to 13 GB

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At this stage, the disk has been resized.  You need to start up your virtual machine and perform changes within the operating system

Step 6 – resize the disk size within the Operating system.

If you open the disk management, you will see that the size of the hard disk has been increased.

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Within the operating system, you will need to perform the additonal operation as required.  You can create a new partition using the additional disk space created or you can increase the size of the existing partition. To resize an exisiting partition, you can follow the procedure that we have decribed in this post

Final Notes

And Voila !   That’s as simple as that.  Proxmox VE and LVM technology provide enough flexibility in order for you to resize in an easy way to resize virtual machines hard disks.  As far as I know, this is the easiest (fastest way) to resize disk files located on a LVM group storage.  Other options/ways exists (such as the dd command) but these methods might not be as effective as the lvresize command.

Till Next Time

See ya

P.S. Dave, I hope this answer your question : -)

 

 

 

 

 

Reference & additonal information:  http://pve.proxmox.com/wiki/Storage_Model