In general, the Azure Virtual machines use the persistent disks. These disks do not affects the data written even after reboots, start, stop or any other lifecycle events. And the data will get saved on the Azure Blob Storage.
But the Temporary disks are not persistent disks, due to which the data written on these disks will get cleared after the VM lifecycle events. This is due to, data for the temporary disks will get stored on the host operating system running the hypervisor software.
- Default Pagefile.sys will be running on the temporary disk.
- The temporary storage is given to store only the temporary data, but not store the data that is relevant to the application or system database files.
- And Microsoft recommends not to use this for application related, as it would risk in losing data and can’t be recovered from any source.
- It is advised not change the drive letter of temporary disk unless it is mandatory for the application hosted on the virtual machine. In such scenario, use the link to https://docs.microsoft.com/en-us/azure/virtual-machines/virtual-machines-windows-classic-change-drive-letter
Possibilities of losing data on temporary storage:
- Resizing a virtual machine
- Updating the host
- Hardware failure on the host
- Re-deploying the virtual machine.