SAS/SATA Compatibility Pays Off

Suresh Panikar, Director, Branded Products Marketing

One of the most important factors in the growth of Serial Attached SCSI (SAS) is its seamless compatibility with Serial ATA (SATA) storage devices. Until the introduction of SAS, choosing a storage infrastructure meant making a choice to which a business would be committed throughout the long life of the infrastructure. This choice usually reflected a compromise between actual storage needs and budgetary considerations, yet it drove the future of the company’s storage infrastructure. Because moving away from the initial decision as needs changed or storage technology evolved always required a tedious and costly upgrade, many companies have clung to an outdated solution that no longer makes sense for their business.

The SAS/SATA compatibility built into SAS components eliminates this long-term commitment to a single storage solution and allows the creation of solutions that can adapt to changing needs with a minimum of cost and complexity. This provides advantages for both end-users and the solutions providers on whom they depend.

Today, data storage has become a SATA universe. SATA’s popularity is built on very attractive per-gigabyte price points in capacities that can easily accommodate the constant data growth businesses face today.

However, while SATA has much to offer as a storage medium, it has several key limitations as a storage environment. Although the disks offer very large capacities, scalability is still limited by a one-to-one relationship between controller ports and storage devices. Expanding beyond that limit requires the installation of additional controllers or Port Multipliers. The known tradeoff in choosing a SATA environment is that it offers less reliability and performance than is typically needed for primary or enterprise-class storage. And, like those traditional storage choices, choosing a SATA infrastructure locks a business into SATA, even if storage needs come to require increased reliability or performance.

Pairing SATA media with a SAS infrastructure overcomes these limitations in a solution that can truly provide long-term investment protection, even as data grows and storage requirements change.

Using a SAS controller allows a storage system that integrates SATA drives to take full advantage of SAS scalability (up to 128 devices) instead of being limited to the number of ports on a SATA controller. So, in an example using an 8-port controller and 500GB SATA drives with a SATA controller, 4TB of total capacity can be achieved. Further expansion requires the purchase and installation of additional controllers. But, an 8-port SAS controller with 500GB SATA drives scales to over 60TB on a single controller.

Integrating SAS controllers, backplanes, and other components with SATA drives provides greater infrastructure reliability than a SATA-only infrastructure. By design, SAS infrastructure components, which are built to minimize failures in enterprise-class, 24 x 7 usage environments, inherently offer greater reliability than SATA infrastructure components. Furthermore, the reliability of SATA drives can also be significantly increased through the use of RAID 6, which protects against two simultaneous drive failures.

The other key benefit of integrating SAS components with SATA drives is long-term investment protection, ensuring the flexibility to adapt that infrastructure simply by changing drives. In fact, no other storage choice a business can make today offers so much flexibility to easily adapt as business needs change.

In a simple example, a business can start with SATA drives, and as additional performance and disk reliability are required, can upgrade them to SAS drives simply by swapping out the drives, without changing infrastructure elements. With a SAS infrastructure, a business also has the ability to mix SAS and SATA drives in a single solution. Thus a storage solution built on SATA disks can be expanded with the addition of SAS disks as needs change, without changing the existing disks.

A business can even build a complete tiered-storage solution that integrates primary and secondary storage within a single infrastructure that integrates both SAS and SATA disks. Expanding or reallocating storage becomes as simple as adding or swapping disks.




Advantages for Solution Providers
SAS/SATA compatibility also pays off for solutions providers. The ability to build such a variety of solutions on a single platform streamlines the qualification process, while reducing the number of base components that must be stocked and supported. The ability to integrate SAS and SATA enables solutions to be better tailored to the customer’s storage and budget needs today, while offering the ability to adapt that solution to maintain customer satisfaction as requirements change. And, when it’s time to upgrade a customer to a fully SAS solution, the necessary infrastructure is already in place, making it much simpler to close the deal.

When it comes to making a storage investment today, a SAS infrastructure is the choice that makes the most sense for the majority of businesses, even if the current storage strategy calls solely for the integration of SATA disks. SAS provides better reliability and scalability for today’s storage needs and provides the only infrastructure flexible enough to accommodate unanticipated storage changes with a minimum of cost and hassle.

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