VM uses disks as a place to store an operating system, applications, and data in Azure. All virtual machines have at least two disks- a Windows operating system disk and a temporary disk. Both the operating system disk and the image are virtual hard disks (VHDs) stored in an Azure storage account. The VHDs used in Azure is .vhd files stored as page blobs in a standard or premium storage account in Azure. Virtual machines can also have one or more data disks that are also stored as VHDs.

Temporary Disk: It is associated with the virtual machine that will be located in the underlying hardware from where the server is provisioned. So, the temporary disk will not be stored in a storage account. It will be stored in the underlying hardware from where this server is located.

Types of Disk

Different kinds of disks that are offered by Azure:

Unmanaged disks: It is a traditional type of disk that has been used by VMs. With these disks, we can create our storage account and specify that storage account when we create the disk. We must not put too many disks in the same storage account, resulting in the VMs being throttled.

Managed disks: It handles the storage account creation/management in the background for us and ensures that we do not have to worry about the scalability limits of the storage account. We specify the disk size and the performance tier (standard/premium), and Azure creates and manages the disk for us.

• Standard HDD disks: It delivers cost-effective storage. It can be replicated locally in one data-center, or be geo-redundant with primary and secondary data centers.
• Standard SDD disks: It is designed to address the same kind of workloads as standard HDD disks, but offer more consistent performance and reliability than HDD. It is suitable for applications like web servers that do not need high IOPS on disks.
• Premium SSD disks: It is backed by SSDs, and delivers high-performance, low-latency disk support for VMs running I/O-intensive workloads. The premium SSD disks are mainly used for production and database servers. So if we are hosting a database in a particular server, then the premium SSD will be a good option.

Microsoft recommends that we should use managed disks for all new VMs and convert our previous unmanaged to managed disks.

Disks backup

When we have this OS disk or data disk associated with Virtual Machine, we need to take the backup of the same regularly so that in case of data risk scenario, we can recover the data.

Azure provides the Azure backup service, which you can install as a backup extension on a particular VM and the extension based on the frequency you specified will take the snapshot off OS disk, and the data disk. And also, at different levels, so we can bring application-consistent snapshots, file consistent snapshots, and these snapshots will be moved into recovery service vault. That's where these snapshots will be stored. In case if something goes wrong with our VM or any particular data center is gone. We can still recover the virtual machine using these snapshots, and if we want to have a geo-redundant ability, then we can have this recovery services vault located in another region.

So for example, if our VM is located in northern Europe, then we can have a recovery service vault located in West Europe. In that way, we can protect our workloads against regional failure also.