Tag Archives: DLS

6 – Non Standard configuration options

Features and licenses

Ever seen these?

License Envelope
License Envelope

If not you might just have thrown away one of the most expensive pieces of you purchase. This is the envelope that contains the transaction key which allows you to generate the license for the specific feature you bought. If you have discarded it I must say that is not really smart. It’s like throwing away the car-keys after you bought a brand new vehicle.

DO NOT THROW AWAY THIS ENVELOPE

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Dynamic Load Sharing (DLS) and In Order Delivery (IOD)

The storage world has always been predictable (from a technical side that is. :-)) This means that data coming from an application through server and traversing a multitude of connected devices to a spindle (in whatever form or shape) takes the logically shortest, fasted and best available route. These routes are calculated based on a protocol called FSPF. (Fabric Shortest Path First) and is somewhat analogous to OSPF in the networking world.

Both OSPF and FSPF are based on Dijkstra’s algorithm of mathematically calculating the shortest path between any two given points. When you fire up Google maps and use the “Directions” option to get a route from A to B the same algorithm is used. Obviously you can adjust the paths between those two points to either include or exclude certain criteria like distance, speed etc. on which you let loose the Dijkstra calculations. To go back to storage the results of the calculations in addition to secondary criteria (zoning, route-costs etc.) determines the routes that are programmed into the ASICs or cross-bar switches. So what does this have to do with load-sharing and delivery ordering??

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