What Are the Business Benefits of SANs?
There`s more than one way to implement storage area networks and network-attached storage.
By Richard Barker
The computing industry is about to go through another major change, catalyzed by high-bandwidth Fibre Channel and scalable switches and hubs. It comes under the umbrella terms of storage area networks (SAN) and the associated concept of intelligent network-attached storage (NAS) devices. In some ways, these technologies are simply natural evolutions of today`s network systems. But they also provide an opportunity to run businesses and systems in a fundamentally different--storage-centric--way.
A SAN is a separate Fiber Channel-based network that connects storage devices to a heterogeneous set of servers on a many-to-many basis. A SAN also enables direct storage-to- storage interconnectivity, separating storage devices from servers and making storage generally available across the network.
In its simplest form, a SAN provides server-to-storage access across fiber--a "SCSI on steroids" capability. However, in a more sophisticated form, a SAN enables disk or tape arrays to be accessed by two or more similar servers at high speeds across Fibre Channel (see Figure 1). This provides immediate performance and connectivity benefits and should eliminate redundant data.
Other benefits include the opportunity to relocate backup, restore, file migration, and data replication processes from servers and local/wide area networks and the ability to move data directly between storage devices across the SAN. This frees up server power for business applications and network capacity for users. These benefits are realized without changing existing applications, database management systems, or user connections to applications via existing local area networks. A SAN simply moves storage from servers to a separate network; applications deliver "local" data-access speed on the SAN, though the data may be many kilometers away.
A NAS device is a box that contains disk or tape arrays. It intelligently manages storage for performance, reliability, and space for one or more servers. A NAS device can be connected via SCSI or file-system interfaces to a SAN to provide storage for multiple homogeneous or heterogeneous servers. These self-managing boxes can also perform local disk-to-tape data transfer without going across the SAN. A NAS device offers heterogeneous access to two or more servers, and the ability to migrate data without affecting any other part of the system (see Figure 2).
In a SAN architecture, availability can be dramatically improved in several ways (e.g., enabling one of several servers to take over for a failed server). RAID technology is inherent in a SAN structure, providing improved reliability and performance. And Fibre Channel and sophisticated switched fabric technology ensure no single point-of-failure on the network. Further, over time, users will be able to replace or repair any component of SAN during normal operation.
Another way of implementing a SAN provides storage-centric connectivity via a LAN or a WAN to application servers (see Figure 3). Each application server connects to a pool of shared on-line, off-line, and intelligent storage devices via the fiber fabric.
Other than data redundancy for resiliency purposes, duplicate data can be removed, saving disk space. Backup, hierarchical storage management (HSM), and replication can then take place within the storage pool and optional NAS devices. Further, should an application server fail, spare servers can take over processing.
Therefore, the benefits of SAN and NAS technology include:
- High-performance access to global data
- Data access from heterogeneous servers
- High levels of scalability
- Ease of management and change
- Cost reduction by removal of duplication
- High availability
So, what does this mean for your business? SANs may enable you to operate in a radically new way, especially if your company is geographically dispersed. Businesses that would potentially benefit include supermarket chains that need to switch pricing on hourly basis or global car manufacturers that needs to cut three months off the production time or defense or health organizations that require ready access to shared data in life-threatening situations. For these organizations, data is the life-blood of the business.
Today, data may be stored in large data warehouses, but it is more likely to be in widely disperse, isolated locations (e.g., data feeds from outside the company, Intranet web sites, multiple applications, and remote databases and email servers). Unmanaged data duplication results in inaccurate information, while isolated data makes it impossible to get a true business "picture" in a timely manner. A SAN provides access to isolated "islands" of data through high-speed network communications.
Another business requirement is continuous data availability. The industry needs to turn in its "system availability" attitude for a "data and application availability" approach.
The SAN model provides automatic data redundancy, automatic backups, and disaster recovery copies. User-level replication can add further resiliency. Clustered servers with shared access to data can dynamically switch users and applications among peer servers, dramatically improving availability.
Companies also require consistent service, that is, the availability of all user applications as well as consistent performance. Here, automated monitoring and management tools are critical, enabling users to identify, isolate, and fix faults without human intervention and without affecting service. Given the scope of SANs, these tools must also be able to monitor trends and pre-empt failures or service problems.
A few years down the road, SANs and related cluster technology will have evolved to the point where all hardware will be able to be replaced on the fly and maintenance will be able to be performed on production systems. Operating system and application software will have to follow suit so that upgrades can be done without bringing systems down.
SAN technology may also prove to be the catalyst for a new breed of global applications. Initial examples may include worldwide Intranet sites that have completely replicated copies of the entire corporate web site on each SAN "continent." These sites would enable subsidiaries or departments to update information locally on the Intranet; all replicas would be updated worldwide shortly thereafter. These applications will create security issues within and across SAN "continents," necessitating new security tools.
SANs will take several years to mature. The key to success is the establishment of a "storage-centric" environment that is supported by a high-performance, low-latency fabric that provides users with highly available access to clusters of application servers with many-to-many connectivity to shared storage.
Figure 1: SANs enable disk or tape arrays to be accessed by two or more similar servers at high speeds across Fibre Channel.
Figure 2: A NAS device offers heterogeneous access to two or more servers, and the ability to do data migration without affecting other parts of the system.
Figure 3: Backup, HSM, and replication can take place within the storage pool and optional NAS devices.