How do SAN and NAS compare in terms of their ability to support a VDI infrastructure, and within a SAN environment, how does Fibre Channel compare with iSCSI?
Both SAN and NAS offer benefits in terms of VDI deployments. SAN infrastructures are high-performance, high-availability platforms that scale well. Today they offer advanced features such as thin provisioning and dynamic block-level tiering. NAS platforms offer the benefits of implicit thin provisioning and file-level cloning. Platforms such as NetApp’s Data Ontap also allows virtual machine cloning within the storage appliance using FlexClones as an alternative to hypervisor-based cloning.
It is not essential to deploy a Fibre Channel SAN in order to support a VDI infrastructure, though it is always assumed that delivering consistent low-latency I/O requires a high-performance storage system using Fibre Channel infrastructure. Other protocols, including NFS and iSCSI, are also suitable for deploying VDI infrastructure solutions. Consideration should be made as to how the overall VDI infrastructure will be deployed. If the storage will be used for both OS and user data, a SAN may be more appropriate than a NAS system as it provides a higher level of availability.
There are solutions on the market (such as Atlantis Computing’s ILIO) that enable VDI solutions to be built using standard SATA drives. They work by translating the random I/O of virtualized servers and desktops into sequential I/O that is more easily managed by lower-performing drives.
You should remember that SANs (irrespective of the protocol used) provide a higher degree of resilience and so are suited to highly centralized environments like VDI.
And, there is no issue with using iSCSI to support VDI deployments. The availability of 10 Gigabit Ethernet connectivity provides the ability to deliver high-performance I/O for all virtualization solutions. Care should be taken in design to ensure that an iSCSI solution provides for the same levels of resiliency and availability as would be deployed in Fibre Channel solutions.
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