The computing industry is about to go through another revolution - the SAN Revolution.
Introduction to SAN
This revolution has been catalyzed by the advent of high bandwidth fibre channel technology and scalable switch/hub technology. It comes under the umbrella terms of Storage Area Networks (SAN) and the associated concept of intelligent Network Attached Storage devices (NAS). In some senses these technologies can simply be thought of as natural evolutions from today's network systems - e.g. faster access across fiber to a storage array. However, in other senses the technology can give us the opportunity to run our businesses and systems in a fundamentally different way - a storage-centric way.
This initiative in the market is being driven by network, storage, server, and storage software companies and by international bodies such as the SNIA and The Fibre Channel Association.
So what is a Storage Area Network?
A Storage Area Network, in its purest sense, is a separate computer network, typically based on a 'fabric' of fibre channel, switches and hubs that connects storage devices to a heterogeneous set of servers on a many-to-many basis. A SAN can also enable direct storage-to-storage interconnectivity, and lends itself exploiting new breeds of clustering technology and to get the best out of Network Attached Storage devices that can intelligently provide disk and tape capabilities to one or more servers.
The technologies that constitute a SAN are as follows. The critical enabler is fiber technology. This is the ability to send data across fibre optic channels at very high speeds and bandwidths to sites as far away as 10 kilometers. Fiber enabled servers, disk arrays and other intelligent storage and other devices are then connected to the "fabric" by fiber through sophisticated switches and hubs. These may be configured in highly scalable manner to provide access from hundreds of servers in many locations to hundreds of terabytes of shared storage resources attached directly to the Storage Area Network. Zoning and other security facilities are emerging to enable the same levels of security that we have come to demand on the mainframe.
What these technologies do is enable the removal of storage devices from their servers and make the storage generally available across the network on a "many to many" basis. In its simplest form SAN simply provides server to storage access across fiber - a "SCSI on steroids" capability. In a more sophisticated form SAN enables a disk or tape array to be accessed by two or more servers at high speed across the fibre channel. The benefits of this include improved performance, greater connectivity and the elimination of redundant data. A Storage Area Network also expedites the use of advanced clustering solutions thereby enabling new levels of availability and business continuity. A SAN also enables us to relocate backup, restore, file migration and replication of data from the servers and local/wide-area networks and have direct data movement from disks/tapes to other disks/tapes across the SAN fiber. The benefits here include:
- Backups done quietly behind the scenes
- Server power is freed up for the business applications
- Network capacity is released for the users
- Remote disaster recovery sites up to date - to the minute!
All this without having to change existing applications, database management systems or the way the user connects to their applications via their current local area network - we are simply moving the storage away from the servers onto its own network. And the applications will be delivering "local" speed of access to data on the SAN where the data may in fact be many kilometers away.
In other words, a SAN represents the removal of storage from their servers and makes the storage generally available across the network.
Increased Flexibility
Isolated data sources can be interconnected and made generally available to multiple servers. The limit for how far apart these sources can be is defined by the enabling infrastructure of the fibre channel itself. This facilitates the re-use of storage in a more efficient manner than ever before. Indeed, through the SAN architecture, we can consider allocating storage from one application to another - even though the applications are running in different physical locations. The result is a far better return on investment from our existing infrastructure.
Improved Scalability
Servers and their associated storage are no longer tightly linked together. New storage devices can be dynamically added to the central pool of storage, without having to add a new server. In a similar way, additional servers can be dynamically added, should we require additional processing power for our applications.
Improved Performance
High performance access to global data is achieved because of the inherent performance characteristics of the enabling fibre channel technology. In addition, the SAN architecture makes it pOSSIble to relocate various activities such as backup, restore, file migration and replication of data. Instead of passing data across the local/wide-area networks via servers, we have the opportunity to move the data directly from disk/tapes to other disks/tapes across the SAN fiber. In this way, server power is freed up for the business applications and network capacity is released for the users.
Improved Availability
The Storage Area Network dramatically improves availability of business processing. For example, any server can take over from a failed applications server - as they share access to the same storage and users. We are no longer constrained by bottlenecks in terms of how we get to our data - we can now reach our corporate data through any application server because of our improved clustering solutions. In addition, data can be automatically replicated to where it is needed in business terms. Technology is now becoming available that will enable such replication to occur at either the disk/volume level or at the database/file-system level. For the really critical applications a change of data value can be updated on all replicas simultaneously - synchronous replication. For most data, however, it is perfectly acceptable that replicas are a few seconds or minutes out of date to their master copy - asynchronous replication. A fundamental utility within the Storage Area Network is a set of facilities to meet these needs. These replication facilities must be completely accurate, reliable exhibit very high performance and thereby give the company confidence to remove all the "private" copies that probably exist to date. Hence the Storage Area Network model provides inherent availability of data the use of automatic data redundancy, automatic backups and the maintenance of nearby recovery copies. User-level replication, as mentioned above, also adds further resilience if provided clustered servers with shared access to the data that can dynamically switch users (and applications between peers will dramatically improve user and business application availability).
Improved Manageability
In many senses Storage Area Networks lend themselves to improved management by their inherently better reliability and "centralization". Whereas previously the storage was "hidden" behind specific servers, it is now generally available. This is inherently safer and simpler to manage - we can now deal with the two separate concepts as such. Automated monitoring and management tools can identify faults, isolate the cause and automatically fix them - without human intervention and with imperceptible effect on the service. Other than data redundancy for resilience purposes, the Storage Area Network enables duplicate data to be removed, saving on total disk capacity needed. Utilities like backup, HSM and replication can then be carried out within the storage pool and any optional Network Attached Storage devices. From a storage perspective things are now much simpler, assisting in ease of use and centrally managed storage policies.
Improved Reliability
Inherent within a SAN structure is RAID disk and tape technology for both improved reliability and performance. Fibre channels and sophisticated switched fabric technology ensure no single point-of-failure on the network component. Further, over time, SAN technology will provide the ability to replace or repair any component during normal operation, reconfigure the system, add new components and otherwise enable the vast majority of changes to be made on the fly.
A Storage Area Network can enable isolated data sources within say a 30 km area to be interconnected and made generally available. Within a Storage Area Network or across one or more interconnected SANs, a most useful capability is automatic controlled replication of critical corporate data to where it is needed in business terms. This may be for a disaster recovery site or to provide local copies for performance reasons. Such replication needs to faithfully reflect the master copy, albeit a few seconds or minutes later. An example might be a corporate Intranet web site with an employer address book that everyone can use in replacement of out-of-date photocopies. And every time you connect to your network your private copy is synchronized on to your computer. Imagine that for corporate data across subsidiaries within a global company.
OSSI is committed to helping companies achieve the benefits of SAN. For more information contact us today!