Arthur Cole spoke with Tom Heil, senior systems architect, Storage Components Division, LSI. Virtualization practically requires a networked storage architecture to support the fluid nature of modern VM and resource management. So why would anyone want to establish a storage network based on direct-attached storage? LSI has come up with a number of reasons, backed by the release of its new line of 6 Gbps SAS switches.
Cole: Some analysts are looking at 6G SAS as a way to introduce networking to direct-attached storage devices. Does this look like a viable solution from your end?
Heil: Yes. In fact, 6 Gbps SAS is the only real way to network direct-attached storage. SAS is ubiquitous as the storage interface in servers and is very prevalent as the back-end or disk connect storage interface in external storage. In addition, SAS is now offered as a front-end or host connect storage interface by the industry's major external storage players. So the need is there. As SAS becomes prevalent in SMBs and data centers, people want to add storage, share the storage and manage the storage. 6 Gbps SAS makes that possible in a DAS environment. The introduction of products like LSI's 6 Gbps SAS switch makes it possible to create a scalable, low-cost storage network in a DAS environment.
"As SAS becomes prevalent in SMBs and data centers, people want to add storage, share the storage and manage the storage. 6 Gbps SAS makes that possible in a DAS environment."
Cole: Would such a network provide functionality equivalent to a SAN or NAS?
Heil: A SAS-based storage network is a very high-performance, low-cost alternative to a traditional SAN, depending on requirements. We fully expect FC and FCoE SANs to continue to be the mainstay of high-end, mission-critical networked storage environments. However, the SAS-based storage network is an excellent approach in several environments.
For bounded environments, such as SMBs and small enterprises, where you want to attach a modest number of servers to a modest number of storage arrays, the SAS-based storage network is ideal. It is a lower-cost, lower-complexity, high-performance alternative to a traditional SAN. This would be a great approach for small environments for video editing, collaborative workstations, etc.
On the other end of the spectrum, in a large enterprise or cloud environment, the SAS-based network can be an in-chassis, in-rack or in-pod storage solution, serving the needs of the blades or servers within that chassis, rack or pod. So what that means is that within each rack, for example, you could have a small SAS SAN acting as local networked storage for that set of servers. So what is driving the application for that type of topology? Data that might be interesting to put there would be server images, applications, OSes. The SAS switch essentially enables server provisioning at a new higher level of granularity -- true stateless servers can be provisioned from a high-speed, low-latency storage fabric.
With respect to the question about NAS, SAS is a block-level interface that doesn't directly serve up files, like NAS does. However, SAS does play a critical role in all NAS architectures as the preferred drive and drive scale-out attach infrastructure.
Cole: How does the zoning feature on the SAS6100 switches work to enhance network functionality?
Heil: Zoning is a critical enabler of SAS as a networked storage solution. The new standardized zoning, defined in the SAS 2.1 specification and implemented on LSI's 6Gbps SAS Switches -- both the LSI SAS6160 and SAS6161 -- enables multiple servers to have shared access to a central pool of storage with isolation between servers to maintain security. So ultimately, standardized zoning enables security, manageability, separation by OS, flexibility and performance. That's why LSI believes the time is ripe for the SAS switch and this type of shared storage solution. The technology supports it and the need is there.