Advanced Server Farm Q&A

Upgrades

Question: Do I need to stop services when I upgrade CSM?

Answer: Certain components of the system can be upgraded without stopping but others require taking everything offline.

Stop the entire farm if you are:

• Upgrading any Cherwell component.
• Changing configuration elements, especially:
  • Connection to the SQL database.
  • Connection to Redis.
  • Logging.

In the following cases do not stop the entire farm, instead take servers offline one (or more, but not all) at a time:

• Changing hardware
• Adding or removing servers
• Installing virus scan on the system
• Installing windows updates

Configuration

Question: Given a high availability configuration, what can go wrong?

Answer: One server in the farm could go down, Redis master could go down, but the server farm remains up and running (provided that there are other web servers running, the Redis master is backed up to a slave, and a sentinel was able to detect the failure of the master). If, as a whole, the load balancer, SQL, or Redis go down, they take down the entire farm, even if the servers in the farm are still running.

Question: How do I know if I have to break up my servers onto multiple machines with a dedicated machine, or if I can share a machine across multiple Cherwell servers?

Answer: Depending on the size of your machine and the performance load you have, a shared machine might not be enough.