QuickStudy: Grid Storage

Contributing Writer, Computerworld |

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Three Basic Benefits

Applying grid topology to a storage network provides several benefits, including the following:

Reliability. A well-designed grid network is extremely resilient. Rather than providing just two paths between any two nodes, the grid offers multiple paths between each storage node. This makes it easy to service and replace components in case of failure, with minimal impact on system availability or downtime.

Performance. The same factors that lead to reliability also can improve performance. Not requiring a centralized switch with many ports eliminates a potential performance bottleneck, and applying load-balancing techniques to the multiple paths available offers consistent performance for the entire network.

Scalability. It's easy to expand a grid network using inexpensive switches with low port counts to accommodate additional servers for increased performance, bandwidth and capacity. In essence, grid storage is a way to scale out rather than up, using relatively inexpensive storage building blocks.

Kay is a Computerworld contributing writer. You can reach him at russkay@charter.net.

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The Grid Storage Difference

Let’s consider a simple network of 16 storage nodes in a high-availability environment, where all nodes require access to one another. The usual way to design this would be with two 16-port switches (the second one for fail-over) in a star configuration. Thus each switch is connected to each of the 16 nodes and each node is connected to both switches, and we have 32 wired connections and two expensive switches. There are two possible paths between any two nodes. If we want to expand the network, we can add more nodes only by also replacing the switches with ones that have more ports available.

Conventional 16-node storage configuration

In a grid arrangement, we could arrange the nodes in four groups of four, each connected to a simple four-port switch. We would also use four additional four-port switches, each connecting to one node in each of the four groups. Now we have 32 wired connections (the same as before), but eight four-port switches instead of two 16-port units, and each node is connected to two switches. In the event of a failure of any of the switches, there are many possible alternate paths to connect any two nodes. The arrangement is more resilient and less susceptible to catastrophic failure than conventional configurations. To expand the network, we can add more nodes and more small switches without having to re-engineer the whole structure. (Note: We could have achieved a similar result by configuring this with four eight-port switches.)

16-node grid storage configuration

Stretching Your Storage Dollars

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Data Center

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