You can use Azure Disk Encryption to achieve encryption at rest for IaaS VMs and disks. It uses the BitLocker feature of Windows for Windows VMs, and the DM-Crypt feature of Linux for Linux VMs, to provide volume encryption for the OS and data disks of VMs in Azure. 

Azure Disk Encryption is also integrated with Azure Key Vault to help control and manage disk encryption keys and secrets. It also ensures that all VM data that is stored on the VM disks is encrypted at reset while it is stored in Azure Storage. Azure Disk Encryption for Windows and Linux VMs is available for Standard VMs and VMs with Azure Premium Storage, and in all Azure public regions and government regions.