WIP - initial draft for Clio

content/concepts/nodes-and-clients/the-clio-server.md

@@ -0,0 +1,60 @@
+---
+html: the-clio-server.html
+parent: concepts.html
+template: pagetype-category.html.jinja
+blurb: Clio is an XRP Ledger API server optimized for WebSocket or HTTP API calls.
+---
+# Clio - the XRP Ledger API Server
+
+Clio is an XRP Ledger API server optimized for WebSocket or HTTP API calls for validated ledger data. 
+
+A Clio server does not connect to the peer-to-peer network. Instead, it extracts data from a specified `rippled` server which is connected to the P2P network. By handling API calls efficiently, Clio servers can help reduce the load on `rippled` servers running in P2P mode.
+
+Clio stores validated historical ledger and transaction data in a space efficient format, using up to 4 times less space than `rippled`.  Clio uses Cassandra or ScyllaDB, allowing for scalable read throughput. Multiple Clio servers can share access to the same dataset, thereby enabling you to build a highly available cluster of Clio servers without the need for redundant data storage or computation.  
+
+Clio requires access to a `rippled` server and the `rippled` need not be running on the same machine as Clio.
+
+While Clio offers the complete `rippled` API, by default, it only returns validated data. For any requests that require access to the P2P network, Clio automatically forwards the request to the `rippled` server on the P2P network and passes the response back to the requestor.  
+
+## Why Should I Run a Clio Server?
+
+There are two main reasons to run a Clio server: lower latency for API requests and lower memory usage.  
+
+A Clio server does not connect to the peer-to-peer network. Instead, it uses gRPC to get validated data from one or more trusted servers that are connected to the P2P network and stores it in a persistent data store. As a result, a Clio server handles requests more efficiently with a lower latency and reduces the load on `rippled` servers running in P2P mode.
+
+
+By using Cassandra or ScyllaDB as the database, the disk requirements for a Clio server are lower as the data is not stored on your local disk.
+
+## How does a Clio Server Work?
+
+{{ include_svg("img/clio-basic-architecture.svg", "Figure 1: How does a Clio server work?") }}
+
+A Clio server stores validated ledger data such as transaction metadata, account states, and ledger headers in a persistent datastore. 
+
+When a Clio server receives an API request, it looks up data from these data stores. For requests that require data from the P2P network, the Clio server forwards the request to a P2P server, and then passes the response back to the client.
+
+
+## See Also
+
+- **References:**
+    - [Commandline Usage Reference](commandline-usage.html) - Detailed information on command-line options for all `rippled` server modes and Clio nodes.
+    - [server_info][] - 
+    - [ledger][] - Manually advance the ledger in stand-alone mode.
+- **Tutorials:**
+    - [Build and Run a Clio node](build-run-clio-node.html)
+    - [Install Clio server on Ubuntu](install-clio-on-ubuntu.html)
+
+# TBD
+
+Run the following commands to install Clio:
+
+```sh
+sudo apt-get update && sudo apt-get install -y wget gnupg2
+wget -q -O - "https://repos.ripple.com/repos/api/gpg/key/public" | sudo apt-key add -
+echo "deb https://repos.ripple.com/repos/rippled-deb-test-mirror focal unstable" | sudo tee /etc/apt/sources.list.d/clio.list
+sudo apt-get update && sudo apt install clio
+```
+
+For more information about running Clio, check out the [README in the Clio project repository](https://github.com/XRPLF/clio).
+
+To report an issue, provide feedback, or propose a new idea, please [open an issue](https://github.com/XRPLF/clio/issues).