For each virtual disk created and attached to the VM, multiple options for disk types exist. Hyper-V has two primary types of disk provisioning methods – fixed and dynamic. Fixed disk format will allocate and zero-write the entire virtual disk onto the underlying storage before continuing with the disk deployment process. Dynamic disks will write stubs to the underlying storage, but only allocates and zero-writes the block on the underlying disk when the in-guest OS attempts to write a block of data onto that previously unwritten block on disk.
For database workloads, fixed disks provide the best possible performance while minimizing the potential fragmentation of the host filesystem objects. An example of the fixed size disk type is shown below.