EVENTHOUGHTHERE are three potential high-availability (HA) scenarios for virtu-al machines (VMs), you still should invest in host clusters. Your level of invest-ment will depend on the hypervisor you choose. Both VMware and Citrix hyper-visors can rely on Network Files System storage to create host clusters. Micro-soft Hyper-V, however, requires the use of either a storage area network (SAN)or an iSCSI target. While SANs may be too costly for small and medium-sizedorganisations, iSCSI is not. For example, you could easily create a shared stor-age subsystem in support of any hypervisor with a standard server—including alarge amount of storage configured in a RAID. By adding iSCSI target software,you can turn the storage server into a low-cost, shared-storage infrastructurethat can support a host failover cluster.
When your shared storage infrastructure is ready, follow the steps outlinedin the table to create a host cluster using one of three hypervisors: Citrix Xen-Server, Microsoft Hyper-V and VMware ESXi. VMs can be created and installedeither before or after you create the host cluster. But it’s important to remem-ber that the files that compose a VM must be located on the shared storagecontainer to enable each host in the cluster to access them.