Schotts Infrastructure Miscellany

May 21, 2007

A few bits of language related to enterprise deployment – someone send me some references, there are probably other, better, names for this:

The differences between “green/blue” and “silver/gold” are subtle, and should probably be generalised.

Green-blue domains

Completely parallel, independent, and symmetric hardware instances at all tiers of an application, only one of which is live at any time. This allows installation/upgrade of applications and data on the non-live partition before switching over the whole partition by just using a load balancer at the front. Releases are alternated between green and blue. The difference between this and having a staging environment is that each of the blue/green environments is production ready, and there are no subtle differences between them that isn’t accounted for.

This patterns allows for frequent, automated, releases at the expense of extra hardware.

Note that, in a variation, green and blue can both run the live application. In this case, you need to isolate green (or blue) before upgrading it. There will be a reduction in redundancy and capacity while this occurs.

Gold-silver data staging

Having data from an upstream process treated as “silver” until verification, and having the current production data treated as “gold”. At some point it is necessary to (as close to atomically as possible) to promote Silver to gold. At the same time, the services used by the previous gold are isolated, and soon after they updated to the new gold data, and joined to production.

Isolation

The process by which a service becomes removed from a pool, and is no longer accessible from the live application

Join

Bringing an isolated server back into a live service set.

Virtual IP switching

A load-balancer supported technique where the pool of IPs associated with a virtual IP is added/removed to. This is one way of isolating/joining a service.

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