Architecting the Virtual Environment: SANs vs. NAS

By Vaughn Stewart, NetApp

In today's virtual environments, one of the most important decisions is whether to deploy a SAN or NAS for the storage infrastructure. This is not a simple decision and there are a number of factors to consider, including price, familiarity, and compatibility with the existing infrastructure.

However, for organizations that are looking to enhance agility and scalability for business-critical applications and cloud services, NAS solutions deliver distinct advantages over SANs. As a result, customers are increasingly choosing NAS over a SAN when deploying storage for virtual environments.

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This isn’t my personal perspective; a number of data points support this view. IDC predicts that by 2015, the storage capacity shipped to virtualized environments attached via a NAS protocol will exceed that attached through all other protocols.1 In addition, with the release of Windows Server 2012, every major hypervisor vendor now supports the use of NAS protocols and enables integrations at the storage layer that are exclusive to NAS.

Here’s how a SAN and NAS compare on performance, agility and scalability.

Performance Is a Must
Before an organization moves its virtualized workloads from a Fibre Channel SAN to Ethernet-based storage, it must be assured that performance won’t suffer. It turns out that a SAN and NAS can deliver identical levels of performance in terms of throughput and latency. Although some still cling to the folklore that SAN must be faster, a number of performance reports refute this outdated view. Performance: No Advantage

Agility Matters
Today’s data centers are populated with multiple hypervisors, and it’s safe to predict that diverse infrastructures will continue to be the norm. However, it’s difficult to predict the mix of hypervisors that may be deployed in the future as the technology advances and licensing models evolve. For this reason, an agile and flexible storage strategy is wise. It can future-proof your infrastructure.

With agility in mind, let’s consider the differences between a SAN and NAS when running multiple hypervisors. With a SAN, the storage object (the LUN) is dedicated to a particular vendor’s platform. The exclusive access to SAN resources results in multiple isolated storage pools, one for each hypervisor. If you needed to migrate a workload between hypervisors, you would face a resource-intensive data migration between proprietary storage containers that would probably include application downtime.

In contrast, NAS is an open, standards-based form of storage connectivity that natively supports multiple hypervisors with shared and elastic containers, a design that allows manageability of the storage container or volume while also providing object-level granularity at the virtual machine (VM) level. This approach provides management efficiencies and simplicity above and beyond that of a SAN.

As business-critical applications are increasingly redesigned to run in highly automated virtual environments, the ability to make rapid changes without disruption to IT operations offers significant value. NAS delivers agility with the flexibility to share pools and implement changes at any time with minimal effort, regardless of how many hypervisors you choose to deploy. Agility: Advantage NAS

Ability to Scale
The ability to scale storage systems for cloud computing and virtual environments has become a matter of management at scale. With average annual data growth rates of 50% and the advent of big data, the ability to scale both capacity and management is paramount. We typically see virtual environments deploy storage pools with densities ranging from 10 to 20 VMs per SAN LUN, while our NAS customers often populate their flexible volumes with 100 to 200 or more VMs. This ability to scale enables storage and virtualization administrators who use NAS to manage significantly fewer storage objects.

The large-scale storage density available with NAS can translate into a tenfold reduction in storage management operations such as replication, backup and recovery, and overall storage resource monitoring. NAS users can also easily increase the size of their data containers without the need for additional support at the hypervisor layer. Scalability: Advantage NAS

Designed for Agility and Scale
Although NetApp offers the option to run either SAN or NAS protocols on our unified, scale-out storage clusters, our experience is in line with IDC’s forecast. Customers are approaching virtualization and cloud computing with the perspective that storage should be a shared, networked service, and they are increasingly choosing to deploy their virtual environments using NAS protocols in order to manage data growth, simplify storage operations and keep their options open in case of future changes.

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1 IDC Worldwide Storage and Virtualized x86 Environments 2012–2016 Forecast, IDC No. 235868, July 2012

Vaughn Stewart, director and evangelist for cloud computing at NetApp

Vaughn is the evangelist for virtualization and cloud computing at NetApp and has been recognized by VMware as a vExpert since 2009. He regularly shares his thoughts on the role of storage and cloud computing in his blog and is co-author of the book Virtualization Changes Everything: Storage Strategies for VMware vSphere & Cloud Computing.

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