Users Guide

22 Designing for High Availability
Storage Configuration
The Dell Storage Solutions Guide for Microsoft Hyper-V provides detailed
information on the various storage configuration options in Hyper-V as well as
best practices for implementing them on Dell storage arrays. This section
discusses the storage considerations in a Hyper-V Host Cluster environment.
Sharing a LUN for multiple HA VMs
A key decision point for Hyper-V Host Clusters is whether each HA VM will
have its own LUN or if multiple HA VMs will share a single LUN. The main
difference between these two configurations is in how they handle failovers.
The NTFS file system grants access at a LUN or volume level and not a file
level. So when an HA VM is moved across physical servers, the ownership of
all the storage LUNs that host that HA VM's files will also transfer across
physical servers. This behavior impacts both planned and unplanned
migrations.
• In planned migration (quick migration) scenarios, if there is a need to
quick migrate an HA VM independent of other HA VMs, then that HA
VM cannot share any of its LUNs with other HA VMs.
Shared Storage • Shared storage is not
required for configuring
the Failover Cluster
• HA VMs will require
shared storage
• Minimum 500MB NTFS
shared disk as Witness
Disk for configuring the
Failover Cluster
•Shared Storage is
required for HA VMs
Requirement to Maintain
High Availability Status
More than 50% of the
nodes must be up for the
cluster to be running
• At least 50% of the nodes
and witness disk must be
available for the cluster
to be running
• If the witness disk is not
available, more than 50%
of the nodes must be
available for the cluster
to be running
Table 3-1. Comparison of Node Majority versus Node and Disk Majority (continued)
Node Majority Node and Disk Majority