docs: Update hosting docs for creating new droplets

Author: Krinkle

doc/hosting.md

@@ -11,11 +11,22 @@ Nodes managed by this Puppet repository are hosted at **DigitalOcean**.
 
 ### Default
 
-* Region: NYC3 (`nyc3-vpc-openjsf1`) or SFO3 (`default-sfo3`)
+* Region:
+  * Most servers should use NYC3 (`nyc3-vpc-openjsf1`).
+  * The exception is critical services (like wp-xx) where we have 2+ servers that are interchangeable (all servers can serve all websites). For that, we also put a server in SFO3 (`default-sfo3`) for increased resilience, allowing us to switch traffic there if needed.
 * Image: Debian (latest LTS).
-* Plan: Typically a small dual-core plan unless more is needed, such as:
-  * Shared CPU > Basic > Regular Intel > 2 CPUs 2GB RAM ($18/month in 2022)
-  * Shared CPU > Basic > Regular Intel > 2 CPUs 4GB RAM ($24/month in 2022)
-* Additional options: Monitoring.
-* Authentication: SSH, add yourself and 1 team mate for initial bootstrapping. These will be replaced by Puppet later.
+* Plan:
+  * When replacing an existing server, pick the same plan the old one unless a spec change is part of the replacement. To see the full spec of an existing server, select it from the "Droplets" list, go to "Resize", and scroll to the highlighted row.
+  * For new servers, we typically use a small dual-core plan unless more is needed, such as:
+    * Shared CPU > Basic > Regular Intel > 2 CPUs 2GB RAM ($18/month in 2022)
+    * Shared CPU > Basic > Regular Intel > 2 CPUs 4GB RAM ($24/month in 2022)
+* Backups:
+  * **Enable** for **puppetserver**, **wpblogs**, and **contentorigin** servers that are in "production", because those are stateful and hard to recreate.
+  * For most servers we leave this off to reduce sponsorship cost, and because they are either not critical (stage servers) or easy to recreate (self-provisioning via Puppet, no state).
+* Authentication: **SSH**. Add yourself and 1 team mate for initial bootstrapping. These will be replaced by Puppet later.
+* Additional options:
+  * Enable "Monitoring" (free)
+* Advanced optoins:
+  * Enable "IPv6" (free)
 * Hostname: Refer to [dns.md](./dns.md).
+* Tags: For production hosts, tag one of "jquery-prod-1cpu", "jquery-prod-2cpu" or "jquery-prod-4cpu" (match the selected plan). This means the server will be included in automatic alerting rules based on server load. We prefer load-average a metric over CPU-utilization, and unfortunately that means the alert threshold varies by CPU count.