How do the leading storage area networking technologies measure up?
Despite a slowdown in IT spending, organisations have continued to create more data than they delete and as a result their storage needs have increased. Most enterprises, government departments and public sector bodies work to maximise value from their data, and one way of achieving this is by networking storage.
Gone are the days when information was created and stored on a direct-attached server; today information is stored on storage area networks (Sans) in order for tens, hundreds or even thousands of users to store, access and share data.
Throughout 2005 the networked storage market has seen the leading technologies consolidate their positions, and three in particular dominated the headlines: 4gbps (gigabits per second) Fibre Channel, Serial ATA and Serial Attached SCSI.
Among the reasons behind the rise of these standards are performance (for 4gbps Fibre Channel and Serial Attached SCSI) and cost (for Serial Attached SCSI and Serial ATA). But these technologies are not mutually exclusive, because - at least today - they have very different applications.
The first, Fibre Channel, is mainly deployed as a transport protocol in the San, but it is also used to connect server clusters, or as a campus backbone, for example. When speed is of the essence, Fibre Channel is the fastest, most scalable and mature storage standard available. This is why it is still the foundation for more than 90% of Sans worldwide.
The latest version of Fibre Channel, 4gbps, enables IT departments to increase productivity by dramatically improving performance (compared to 2gbps) while reducing costs by halving the number of required ports and host bus adaptors.
In addition, 4gbps Fibre Channel can be deployed to increase performance when carrying out data replication over the local San. For example, if several arrays are replicating to a single 4gbps, this will be able to handle a larger load, thus preserving replication performance.
Another major attraction of this variety of Fibre Channel is that it is fully compatible with its 2gbps and even 1gbps predecessors. And even though 4gbps devices will run at the lowest common speed, thanks to zoning, it is possible to maximise performance, carry out a gradual upgrade and protect existing investment. In addition, 4gbps systems are similar in price to 2gbps systems.
The main appeal of Serial ATA, which has been around for a while and runs at 1.5gbps, rests in its low cost - it was initially created with desktop cost in mind.
Serial ATA technology is ideal for storing secondary copies of data and hence it is popular for applications such as disc-to-disc back-up. Looking at the information lifecycle pyramid, Serial ATA can be found towards the base, above tape and below SCSI. Organisations deploying Serial ATA have found that upgrading and configuration are relatively easy.
An added bonus is that Serial ATA infrastructure is compatible with Serial Attached SCSI - both systems' discs can easily fit in the same cabinet without the addition and expense of bridges to convert from one to the other. Where Fibre Channel and Serial ATA are in the same array, a bridge is necessary.
Like Fibre Channel and Serial ATA, Serial Attached SCSI provides increased device support and bandwidth scalability.
Mainly deployed inside the array, Serial Attached SCSI is the latest variety of the ubiquitous SCSI technology.
With its combination of enterprise performance, simplicity, reliability and low cost, Serial Attached SCSI is the ideal successor to SCSI. At 3gbps, this ratified standard is a compelling choice for connection inside the array, where users require the flexibility of performance, capacity and low cost - Serial Attached SCSI prices are similar those for SCSI.
Serial Attached SCSI products, namely discs, host bus adaptors and expanders, have already appeared with discs coming in both the traditional 3.5 inch and SFF (small form factor) sizes to provide even more flexibility and scalability. Like Fibre Channel, Serial Attached SCSI provides enterprise-class robustness, reliability and peace of mind, and thanks to its compatibility with both SCSI and Serial ATA, it offers investment protection and therefore a high return on investment.
This year has been an exciting time for organisations looking to upgrade their Sans or taking the plunge for the first time. Networked storage is now a mature architecture offering users tools to build the most efficient and cost-effective systems tailored to their specific needs.
Technologies and architectures will evolve and consolidate over time to offer ever-greater benefits. The first step for organisations will be to take a close look at their requirements and identify the most suitable standards and topologies for their environment and grow from there.
Paul Talbut is chairman of the Storage Networking Industry Association Europe