Creating and configuring an additional disk on an instance

Find out how to attach a new volume to your Public Cloud instance

Last updated 4th January 2023


It is possible to create additional disks for your Public Cloud instances. This can be useful in cases where:

  • You want to increase your storage capacity without changing the instance model.
  • You want to have a highly available, high-performance storage.
  • You want to move your storage as well as your data to another instance.

This guide explains how to create an additional disk and configure it on your instance.


This feature is currently not available for Metal instances.


Attaching a new volume

Log in to the OVHcloud Control Panel and open your Public Cloud project. Then open Block Storage in the left-hand menu.

In this section, click on the button Create a volume.

select project

Follow the configuration steps in order to select options for location, disk type and disk capacity. Then enter a name for the volume and confirm by clicking on Create the volume.

create disk

The new disk will now be displayed in the Control Panel.

configure disk

To the right of the volume, click on the ... button, then select Attach to instance.

attach disk 01

In the popup window, choose an instance from the list and click on Confirm to attach the disk.

attach disk 02

The process of attaching the disk to your instance will now begin. This may take a few minutes to complete.

Make sure to not leave the current page in your OVHcloud Control Panel while the disk is being attached. This might interrupt the process.

Configuring the new disk

The examples below presume you are logged in as a user with elevated permissions.

Using Linux

Establish an SSH connection to your instance, then use the command below to list the attached disks.

~$ admin@server-1:~$ lsblk

vda 254:0 0 10G 0 disk
└─vda1 254:1 0 10G 0 part /
vdb 254:16 0 10G 0 disk

vda in this example refers to the default disk of the instance. The additional disk will then be labelled vdb.

Create a partition on the additional disk using the commands below.

~$ admin@server-1:~$ sudo fdisk /dev/vdb

Welcome to fdisk (util-linux 2.25.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x95c4adcc.
Command (m for help): n

Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p):
Using default response p.
Partition number (1-4, default 1):
First sector (2048-20971519, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-20971519, default 20971519):

Created a new partition 1 of type 'Linux' and of size 10 GiB.
Command (m for help): w

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Next, format the new partition vdb1 using the command below.

~$ admin@server-1:~$ sudo mkfs.ext4 /dev/vdb1
mke2fs 1.42.12 (29-Aug-2014)
Creating filesystem with 2621184 4k blocks and 655360 inodes
Filesystem UUID: 781be788-c4be-462b-b946-88429a43c0cf
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

Mount the partition with the following commands:

admin@server-1:~$ sudo mkdir /mnt/disk
admin@server-1:~$ sudo mount /dev/vdb1 /mnt/disk/

Finally, check the mount point using this command:

~$ admin@server-1:~$ df -h

Filesystem Size Used Avail Use% Mounted on
/dev/vda1 9.8G 840M 8.6G 9% /
udev 10M 0 10M 0% /dev
tmpfs 393M 5.2M 388M 2% /run
tmpfs 982M 0 982M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 982M 0 982M 0% /sys/fs/cgroup
/dev/vdb1 9.8G 23M 9.2G 1% /mnt/disk

The mounting is not persistent because the disk will be detached when the instance reboots. In order to automate the mounting process, the fstab file needs to be edited.

First, retrieve the UUID (block ID) of the new volume:

~$ admin@server-1:~$ sudo blkid

/dev/vda1: UUID="51ba13e7-398b-45f3-b5f3-fdfbe556f62c" TYPE="ext4" PARTUUID="000132ff-01"
/dev/vdb1: UUID="2e4a9012-bf0e-41ef-bf9a-fbf350803ac5" TYPE="ext4" PARTUUID="95c4adcc-01"

Open /etc/fstab with a text editor:

~$ sudo nano /etc/fstab

Add the line below to the file and replace the UUID with your own:

UUID=2e4a9012-bf0e-41ef-bf9a-fbf350803ac5 /mnt/disk ext4 nofail 0 0

Save and exit the editor. The disk should be automatically mounted after every reboot from now on.

Using Windows

Establish a remote desktop (RDP) connection to your Windows instance.

Once logged in, right-click on the Start Menu button and open Disk Management.

disk management

The new disk will be displayed as an unknown volume with unallocated space.

unknown volume

If the disk is marked as offline here, it needs to be initialised first. You can use the Windows GUI or the DISKPART utility to achieve this. Otherwise, proceed with formatting the disk in Disk Management.

Initialising the disk in Disk Management

Right-click on the disk and select Online.

If the disk is marked as offline here, this is likely due to a policy in place on the instance. To fix this, right-click on the disk and select Online.

offline disk

Then right-click it again and this time select Initialise Disk.

offline disk

Next, select MBR and click OK.

initialise disk

Initialising the disk with DISKPART

Right-click on the Start Menu button and open Run.

initialise disk

Type cmd and click OK to open the command line application.

run prompt

At the command prompt, open DISKPART:

C:\> diskpart

Use the following series of DISKPART commands to set the disk to online:


SAN Policy : Offline Shared
DISKPART> san policy = OnlineAll

DiskPart successfully changed the SAN policy for the current operating system .

- Implementation of the strategy on the extra disk:
[Code] DISKPART> list disk

Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 200 GB 0 B
* Disk 1 Offline 10 GB 1024 KB
DISKPART> select disk 1

Disk 1 is now the selected disk.
DISKPART> attributes disk clear readonly

Disk attributes cleared successfully.
DISKPART> attributes disk

Current Read-only State : No
Read-only : No
Boot Disk : No
Pagefile Disk : No
Hibernation File Disk : No
Crashdump Disk : No
Clustered Disk : No
DISKPART> online disk

DiskPart successfully onlined the selected disk.
Formatting the disk

In Disk Management, right-click on the new disk and select New Simple Volume....

format disk

In the wizard, click Next to specify the volume size. It should be set to maximum by default. Click Next to continue.

format disk

Leave the new drive letter at default or select a different one, then click Next.

format disk

Label the volume (optional) and confirm the formatting options by clicking Next.

format disk

In the last window, click Finish to format the disk.

format disk

The disk will be available as a drive in File Explorer after the operation.

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