Duncan Epping of the highly talented VMware employee pool and Yellow Bricks stardom has released for us a great VMware High Availability (HA) Implementation Notes document. In it, you will find some advanced configuration options for VMware HA – real good stuff that is sure to put your significant other to sleep.

Throughout the document, “das.” appears. What is das and what does it have to do with high availability? For the sake of my kids (whom I hope grow up to be virtualization evangelists and successors to my blog), I’ll explain. Back in the days of the VI3 beta, DAS was an acronym for Distributed Availability Service. But it was not to see the light of day, for VMware often becomes discontent with technology names and acronyms, usually after the labels have already been permanently etched in documentation, books, hundreds or thousands of lines of code, and our brains.

• .dsk files became .vmdk files
• DAS became HA
• ESX Server became ESX
• Most recently, Continuous Availability became FT (Fault Tolerance)

So as seen in the examples above, DAS is nothing more than the “old” name for HA. Apparently, there is more to updating code than using “find and replace” so VMware opted to leave das. configuration instances in the HA product that exists today.

It’s hard to second guess the creative minds at VMware.  Maybe they thought DAS would be confused with DRS which was releasing at the exact same time.  They would have been right.  There are still people walking around today that explain DRS as “Dynamic Resource Scheduler” which is incorrect and drives me up the wall.  Distributed.  Distributed.

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