What Is a Storage Area Network (SAN)?
A storage area network (SAN) is a dedicated high-speed network that makes storage devices accessible to servers by attaching storage directly to an operating system. It centralizes storage devices so they are easier to manage and communicate faster over media.
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Why are SANs essential to today's businesses?
SAN storage has been around for many years. But several factors are making this network-based storage solution more important than ever for everyday business use. For example:
- Organizations need to provide users reliable access to data at all times.
- Data of all types, structured and unstructured, is growing exponentially.
- Cloud computing, digitization, and other IT trends are placing higher demands on the technology used to manage, transport, back up, and restore data.
Also, organizations have more diverse application environments, and they want to avoid storage access issues that can undermine application performance.
Growing adoption of new technologies to support newer app environments — such as high-performance storage systems with Non-Volatile Memory Express (NVMe) — is also placing pressure on storage networks.
Many organizations are also more focused on disaster recovery and business continuity today and want to consolidate data into a SAN network to make data replication easier.
In short, organizations need to ensure the SAN they rely on to accelerate their access to data and support increasing application workload availability and performance requirements is modern and designed to meet new challenges.
What is SAN fabric?
SANs provide any-to-any connectivity for servers and storage devices using Fibre Channel (FC) switches that are compatible with the FC protocol. FC SAN switches are used to connect devices within a SAN to create the SAN fabric.
Routers, gateway devices, and cables that help the SAN interconnect servers with storage devices are also part of SAN fabric. IT teams can use fabric layer elements to optimize the performance, scalability, and availability of the SAN for the business and its users.
There are two additional layers in the SAN that are not part of the SAN fabric:
- The host layer, which is comprised of the servers that attach to the SAN to access data from storage devices to support application and database workloads
- And the storage layer, which includes all the storage resources that the SAN brings together into one network, including disk arrays, tape arrays, flash solid-state drives, RAID arrays, and more.
How do SAN and NAS differ?
A SAN and network-attached storage (NAS) are both network-based storage solutions; however, a SAN is more complex.
A SAN is a network that operates independently of an organization's operating system and is comprised of many different storage devices. It uses FC switches and stores data at the block level. To a client operating system, the SAN typically appears as a disk.
A NAS device, or NAS unit, connects to a local-area network (LAN) through an Ethernet connection to provide file-based data storage services to other devices on the network. To a client operating system, a NAS device appears as a file server.
While NAS also takes storage devices away from the server to create a central pool of data, NAS storage connects directly to the LAN. In SAN storage, capacity is pooled and provided with a dedicated network.
Is modernizing a SAN disruptive?
It doesn't have to be. If an organization already has the right SAN infrastructure in place, it can work with a leading provider of SAN technology to modernize its storage area network seamlessly and quickly, and without a major equipment upgrade.
The business can also invest in today's SAN technology that can evolve to keep up with increasing application workload availability and performance requirements. That can help the business avoid forklift upgrades for its SAN infrastructure in the future as needs change.
Learn more about how organizations can modernize their SAN fabric and make the most of existing infrastructure assets in the ESG white paper "Optimize, Accelerate, and Simplify SANs Non-Disruptively with Cisco MDS."
Features and capabilities in a modern SAN
Security, reliability, availability, flexibility, and scalability are all hallmarks of a modern SAN, and necessary for optimal performance.
But organizations that want to help ensure they're investing in a solution that will help them increase performance of their storage infrastructure today and for the future will also want to look for SAN solutions that offer advanced features and capabilities, such as the following:
Real-time visibility and analytics
An advanced SAN solution offers built-in, hardware-based analytics that provide complete visibility across the SAN in real time. This insight enables fast troubleshooting and improved operations. It also provides clear evidence as to whether the SAN or storage is creating performance issues in the network.
Operational simplicity
Intelligent SAN technology promotes operational simplicity by bringing programmability, analytics, manageability, and visibility to the SAN. Ideally, IT and storage admins should have end-to-end visibility into the SAN through a single-pane-of-glass view to facilitate effective health monitoring, diagnostics, and troubleshooting of the storage area network.
Also, SAN infrastructure that includes DevOps tools like Ansible can make end-to-end provisioning significantly faster and easier. It can also help businesses reduce their operational expenditures (OPEX).
Congestion mitigation
Congestion in a SAN fabric occurs when there is more data to deliver to a device than the device itself can absorb. This leads to performance degradation. Congestion can occur for two key reasons: First is a condition known as slow drain; the second is overutilization.
A recently released software innovation called Dynamic Ingress Rate Limiting (DIRL) identifies and prevents SAN congestion. The DIRL software prevents congestion caused by slow drain and overutilization, without any impact on the target device and other connected devices. DIRL resolves the root cause of congestion by dynamically adapting traffic to alleviate egress congestion on the network.
FC switches in the SAN that feature DIRL can rate limit an interface from about 0.01 percent to 100 percent of its maximum utilization. Also, they can adjust the interface rate dynamically up or down based on detected congestion conditions.
Another consideration: 64G readiness
SAN solutions must be able to evolve continually to keep up with increasing application workload availability and performance requirements. So, when modernizing their SAN, organizations will want to look toward the future for solutions that are ready for 64G FC performance, without the need for a major equipment upgrade.
64G FC is a high-speed data transfer protocol. Adopting SAN infrastructure that is 64G-ready can provide an organization with peace of mind. It's a forward-looking investment that can translate to significant savings in capital expenditures (CAPEX). The ability to maintain continuity in application delivery can also create many business benefits.