What is the best approach for zero downtime deployments for Multi-Site implementations?

Question

I have a Single Sitecore Instance, where multi-site implemented for 3 countries.

- Content
   - Country 1
       - Home 
       - About Us
   - Country 2
       - Home 
       - About Us
   - Country 3
       - Home 
       - About Us


1. Country 1    (www.example.c1)
2. Country 2    (www.example.c2)
3. Country 3    (www.example.c3)

During deployment

1. If any deployment done to Country 1 website, expecting only the Country 1 website to have the down-time, the other sites should have 'Zero downtime & impact'

To achieve this, what is the best practice to be followed ?

1. A separate IIS website & app pool needs to be created for each country ?
2. A separate folder for each website, in which the binaries needs to be deployed ?
3. What is the Sitecore license implication ?

Answer 1

To achieve zero downtime for sitecore websites, a commonly recommended "best-practice" approach is to have two sitecore Content Delivery (CD) servers and a load balancer in front, and then a separate CM server for content management. This approach also works perfectly for your multisite scenario because all 3 sites are served from both CD servers (one app pool in each, with all site bindings). Any deployment can be done by taking one CD server offline (removed from load balancer) at a time, updating the code, then bringing online and repeating this for the other server, always having one CD server online and resulting in zero downtime.

Note that sitecore licensing typically requires that you have a license per instance (and different app pools also count as separate instances, so contact sitecore to discuss your licensing requirements).

The examples you suggested are not best practice, but could be considered to reduce costs. You could have 3 separate app pools serving separate sitecore CD instances (each its own website folder on disk with a full copy of the website files/binaries), the only difference would need to be a unique config "Analytics.ClusterName" setting. This means you don't need extra infrastructure, but this will share the resources of the server and possibly result in slower performance, and still need to be licensed as separate instances. Then the site bindings in IIS for each country's website can each be binded to one app pool.

Note that you should use the sitecore standard single instance (combined CM/CD) configuration for multiple instances. They should be configured as CD instances, so that they don't all do the same processing jobs that will conflict with each other and result in a broken application!

Answer 2

In order to achieve Zero / No downtime while deploying the country specific websites, there could be two possible solutions:

1. Use two or more content delivery servers with load balancer. You can deploy in each server one by one. For example, take one server down from the load balancer (remaining servers still serves the requests) and deploy ot it and once deployment is complete, connect this server back to the load balancer.

   Repeat the same steps with other content delivery servers.

2. Use cloud solutions for highest website availability.

Either of the above approach, will give you zero downtime when you deploy your country specific websites.

Hope this helps!