Document history expiry

Author: yorickdowne

website/docs/Support/HelpfulWebsites.md

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 title: Helpful Websites
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website/docs/Support/Prune.md

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 title:  Windows
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website/docs/Support/Windows.md

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 title: IPv6
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website/docs/Support/ipv6.md

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 title: "Choose a Grafana dashboard (optional)"
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website/docs/Usage/Dashboards.md

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 title: Resources, hardware
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website/docs/Usage/Hardware.md

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 title: "Create and import validator keys to the client"
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 sidebar_label: Import Validator Keys
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website/docs/Usage/ImportKeys.md

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 title: Linux security and setup recommendations
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website/docs/Usage/LinuxSecurity.md

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 title: Networking and port forwarding
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website/docs/Usage/Networking.md

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+---
+title: Archive, Full or Expired node
+sidebar_position: 2
+sidebar_label: History and Pruning
+---
+
+## Types of nodes
+
+You can run an Archive node, with all history and full lookup for all historical transactions. This may take large amounts of space, depending on the execution layer client.
+
+You can run a Full node, with all history and limited lookup for historical transactions. This fits into a 4TB drive and is often the choice for RPC nodes.
+
+You can run an Expired node, with pre-merge history and receipts gone. This fits into a 2TB drive and is foten the choice for validator nodes.
+
+This is controlled by variables in `.env`, which can be set with `nano .env`. Switching from one type to another often requires a full resync.
+
+`CL_ARCHIVE_NODE` - run the consensus layer node as an archive, including blobs where supported  
+`CL_MINIMAL_NODE` - run the consensus layer node with minimal storage
+
+`EL_ARCHIVE_NODE` - run the execution layer node as an archive. The required space can vary widely depending on the client: From right around 2 TB to well over 50TB  
+`EL_MINIMAL_NODE` - run the execution layer node with history expiry. `true` is pre-merge history expiry; `rolling` is 1-year rolling if the client supports it;
+`aggressive` expires all but the last few blocks, if the client supoorts it
+
+## Switch from Full to Expired node
+
+You can use `./ethd prune-history` to switch the client to history expiry, in some cases without resync. Note that Besu requires 200 GiB free for this, and
+it will take less space if instead it is resynced with `./ethd resync-execution` while `EL_MINIMAL_NODE=true`
+
+## State pruning
+
+In addition to history, execution layer clients also carry state. Historically, the size of the state DB has been growing and can be pruned periodically.
+Today, only Nethermind still requires a state prune. Note this is entirely separate from history expiry. It applies to Full and Expired nodes. Archive
+nodes should never have their state pruned.
+
+### Automatic Nethermind prune
+
+By default, Nethermind will prune when free disk space falls below 350 GiB on mainnet, or 50 GiB on testnet. If you
+want to disable that, `nano .env` and change `AUTOPRUNE_NM` to `false`.
+
+If you have disabled automatic prune, you can run `./ethd prune-nethermind`. It will check prerequisites, online prune Nethermind, and restart it.
+
+### Continuous Besu prune
+
+Besu continuously prunes with BONSAI, and from 24.1.0 on also prunes its trie-logs. A long-running Besu may benefit
+from a manual trie-log prune, once.
+
+If you have a large amount of trie logs, run `./ethd prune-besu` on a  long-running Besu. It will check prerequisites, offline prune Besu trie-logs, and
+restart it.
+
+### Continuous Geth prune
+
+Geth continuously prunes if synced with PBSS. If you are using an old hash-synced Geth, run `./ethd resync-execution`
+to use PBSS. This will cause downtime while Geth syncs, which can take 6-12 hours.