Docker Containers
Although Docker containers appear to be like Virtual machines, however for me the container tech has totally changed the way I think about compute nodes.
When we shifted from Physical machines to Virtual machines the overall feeling was that we were saving tons of time and money by consolidating multiple machines on reduced number of hardware and at the same time unutilized resources were being put to good use. Overall a really good switch for the business owners by reducing costs and also for engineers by reducing the number physical machnies to maintain ( with the flip side of More number of VMs to manage for the SysAdmin ).
Anyway so VMs are extremely good at what they do. You can even pin resources on critical VMs, take snapshots, apply network policies, make Highly available architectures. But if you have invested so much time in a VM you will think twice before deleteing that VM, atleast I will. And thats where the Container technology is different from the VM.
You run one container from an image or a thousand containers from that same image with same settings. So one needs to spend time to carefully craft an image with all the dependencies required and then build that image. After that create and destroy as many containers as required!
Some days ago I had to test an HAProxy cluster. Used docker to complete a three node testing in no time at all. Amazing tool to perform testing.
There is however another debate about stateful and stateless containers. IMHO statefull containers dont really make that much sense for me, may be keep using VMs for that kind of workload instead of using containers :D .
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