Advantages and disadvantages of using a SAN

Advantages of a storage area network

• Fast.
• Easy to scale.
• Fault-tolerant.
• Better hard disk utilization.

One of the biggest advantages of using a storage area network is that SANs generally provide better performance than competing technologies, such as network-attached storage (NAS). A NAS is a network-based storage device, with storage traffic being routed across a LAN. NAS systems are typically inexpensive -- with some consisting of only a single hard drive -- and easy to configure. However, NAS devices tend to be slow because they are constrained by network bandwidth limitations. Even so, they remain a popular choice -- especially in smaller environments -- for use as file servers or as a general-purpose data storage platform. Some organizations also use NAS devices for data protection.

SANs, on the other hand, are purpose-built networks designed specifically for enterprise storage. Rather than sending storage traffic across a LAN, SAN traffic is usually sent over a dedicated Fibre Channel connection. Servers have direct, block-level data access to storage devices within the SAN. The result is better performance than what can typically be achieved through a NAS or similar technology.

SANs are also designed to be easy to scale. An organization can add capacity simply by adding switches and hard disks. However, scalability can include high costs at the enterprise storage level.

Another advantage of using a SAN is that it helps organizations to use their raw storage more efficiently. Consider that when direct-attached storage (DAS) is used, each server has its own disks, spanned by a file system. Because it's almost impossible to estimate the exact amount of storage space that a server will need, some amount of capacity will likely go unused. Conversely, SANs treat storage space as a pool of resources that can be allocated on an as-needed basis. This helps avoid wasted capacity.

SANs are specifically designed for use in high-performance, mission-critical environments. As such, they typically include multiple levels of redundancy. For instance, if a switch fails, storage traffic is automatically rerouted through another switch to avoid an outage.

Disadvantages of a storage area network

SANs have two main disadvantages. First, they are expensive. Redundant, high-performance hardware is costly by its very nature. However, it isn't just the acquisition costs that make SANs expensive. There are also ongoing maintenance and management costs to consider.

The other main disadvantage to operating a SAN is its complexity. Deploying, managing and maintaining a SAN requires special knowledge. As such, organizations that deploy SANs must provide the IT staff with additional training or hire storage administrators.

Specific cost and complexity concerns include:

• High initial investment (capital expense).
• High cost of scalability.
• Complex configuration makes initial setup and troubleshooting difficult.
• High cost of configuration and administrative talent to deploy and maintain the SAN.
• Potential single point of failure.
• Vendor lock-in risk tied to proprietary hardware and protocols.

In many organizations, these concerns are outweighed by the advantages a robust SAN deployment offers. However, the challenges are worth noting, particularly around long-term configuration and troubleshooting support. Scalability is also a very real issue.

Decision-making guidance

SANs can deliver high performance, centralized storage and enterprise-grade availability, but they are not always the right fit. Begin by defining business objectives to identify the actual issues the SAN should resolve. Ask the following questions:

• Are mission-critical applications dependent on low-latency storage?
• Is downtime financially or operationally unacceptable?
• Is rapid business growth (and, therefore, storage requirements) expected?
• Are regulatory or compliance requirements driving infrastructure decisions?
• Does the organization require centralized storage governance?

SANs are often a good choice when specific decision criteria are met, such as:

• Running large databases, virtualization or transactional systems.
• Supporting 24/7 operations.
• Managing large-scale virtualization clusters.
• Requiring high availability and disaster recovery.

SANs may not be a good choice when the following criteria apply:

• Workloads are lightweight or departmental.
• The primary need is file sharing.
• Cloud-native applications dominate.
• Budgets (CapEx and OpEx) are constrained.

Common use cases

Database hosting is a common use case for SANs. Mission-critical applications almost always rely on back-end databases. SANs help ensure that these databases deliver the required level of performance while also helping to protect the data within the databases.

SANs are also commonly used in virtual server deployments. Server virtualization is based on the idea that physical servers are commonly underutilized and that hardware costs can be decreased by allowing multiple virtual servers to share a physical server's hardware resources. The flip side to this, however, is that VMs compete with one another for access to hardware resources and, if left unchecked, can overwhelm a host. This is especially true for storage IOPS, which tends to be the resource that most often limits the number of VMs that a host can accommodate.

A SAN can help to increase a host's virtual machine (VM) density by offloading storage resources from a local storage device. Additionally, a SAN is designed with multiple layers of fault tolerance and can, therefore, help to make VMs more resilient to failure.

Just as SANs can benefit virtual server environments, a storage network can also benefit organizations that host virtual desktops. VDI environments are somewhat like virtual server environments, but they host desktop operating systems such as Windows 11 rather than virtual servers. A VDI platform may host hundreds, or even thousands, of virtual desktops. A SAN can be an ideal storage platform for VDI environments because it can easily scale to accommodate additional virtual desktops as an organization grows.

Reasons not to use a SAN

Even though SANs offer several compelling benefits, there are several important reasons to consider not using a SAN. A SAN is a poor choice if an organization lacks the financial resources to purchase, deploy and maintain it. Even if an organization can afford a SAN, it must consider the effect that a SAN deployment will have on its IT budget. If other costly IT projects take a higher priority, then the SAN deployment might need to wait until next year.

SAN solutions are not typically a good fit for organizations moving toward hybrid cloud or cloud-first initiatives. Modern alternatives such as hyperconverged infrastructure and cloud-native storage platforms increasingly offer simpler operational models with lower management overhead. Development projects that rely heavily on containerization and stateless deployments are also not likely to benefit.

Another reason not to use a SAN is that the organization's IT architecture simply does not justify it. A SAN probably isn't warranted, for instance, if an organization only has a few servers.

Finally, an organization might not want the complexity of a SAN if it lacks the IT staffing resources to properly support it. Supporting and managing a storage network requires a certain amount of expertise. Unless an organization has the necessary expertise, it is likely better off adopting a different storage option.

The best IT decisions, including those about SAN solutions, are rarely about technology alone -- they are about balancing:

• Performance.
• Risk.
• Cost.
• Operational maturity.
• Long-term business strategy.