Planned and unplanned downtime
Shared Nothing Live Migration protects you from planned downtime, such as patching Windows on a host or replacing or upgrading hardware components. See:
For an unplanned downtime you need either VM HA (little downtime, little data loss, VM reboots) or guest VM cluster (no downtime, no data loss, VM turns to other host). See:
Shared storage options
Both require some sort of physical or virtual shared storage. For physical storage, you may need CSV configured on Clustered Storage Spaces, iSCSI, FC SAN, or an SMB3 share. See:
| Storage Type | Description |
|---|---|
| Shared virtual hard disk | New in Windows Server 2012 R2, you can configure multiple virtual machines to connect to and use a single virtual hard disk (.vhdx) file. Each virtual machine can access the virtual hard disk just like servers would connect to the same LUN in a storage area network (SAN). For more information, see Deploy a Guest Cluster Using a Shared Virtual Hard Disk. |
| Virtual Fibre Channel | Introduced in Windows Server 2012, virtual Fibre Channel enables you to connect virtual machines to LUNs on a Fibre Channel SAN. For more information, see Hyper-V Virtual Fibre Channel Overview. |
| iSCSI | The iSCSI initiator inside a virtual machine enables you to connect over the network to an iSCSI target. For more information, see iSCSI Target Block Storage Overview and the blog post Introduction of iSCSI Target in Windows Server 2012. |
Virtual SAN without physical shared storage
For virtual storage, you may use either a solution running inside a VM, which is slower and raises a dependency problem, or a native virtual SAN.
See:
Virtual SAN (no hardware storage)
You'll have a configuration similar to this picture (below). See:
Historical diagram pending restoration.
So no physical shared storage, SAN emulated from DAS. High performance (no network I/O) and fault tolerant (even with a pair of nodes all components are at least duplicated).