Users Guide

Designing for High Availability 23

• In unplanned migration scenarios, this might be a factor depending on the

resource requirements for all the HA VMs that share a LUN. If the cluster

service is unable to successfully bring all the HA VMs (that share the single

LUN) online on another node, it will retry on all other available cluster

nodes. If none of the available cluster nodes can host all the HA VMs due

to resource constraints, it is likely that none of the HA VMs that share the

single LUN will be brought online

Table 3-2 shows important factors to consider when planning to share a LUN

across multiple HA VMs:

Table 3-2. Determining if a LUN can be Shared

NOTE: Depending on the Disk I/O in the specific configuration, sharing a single

LUN across multiple HA VMs may also impact I/O performance.

Storage Options for Hyper-V Host Clustering

The type of storage that is used in a Hyper-V Host Cluster will most impact

the design of the Hyper-V Host Cluster solution. It will affect:

• The number of network adapters on each Hyper-V host

• The number of storage adapters on each Hyper-V host

• Quick Migration because VM state is saved to disk over the storage fabric

Table 3-3 summarizes the different types of storage that support Hyper-V

Host Clustering and Hyper-V Guest Clustering. For a full list of supported

storage hardware for Hyper-V, refer to the Dell Storage Solutions Guide for

Microsoft Hyper-V.

Single LUN can be shared by multiple HA

VMs

Single LUN is required per HA VM

• If the HA VMs are only using VHD-

based virtual hard disks (and not

passthrough disks)

and

• If it is acceptable that all HA VMs will

move across hosts simultaneously in

planned failover scenarios (Quick

Migration)

• If the HA VMs are using passthrough

disks (and not VHD-based virtual hard

disks)

• If there is requirement to be able to

migrate HA VMs one at a time in

planned failover scenarios (Quick

Migration)