Blog post

UTxO-HD will have an impact on the Cardano node performance for no apparent immediate benefit. We need to:

Explain why UTxO-HD is important for the long-term sustainability of the Cardano node.
Warn about the expected performance loss.
Explain the problem and solution
Implications of not solving the problem, in particular, what would the mem requirements be.
Explain what this means for sustainability and decentralization.

We need performance metrics so that the community can make an informed decision.

We will relay this information in the form of a draft blogpost to the Cardano Steering Committee.

Checklist

[x] #151
[x] Develop documentation for other developers/teams (inc. READMEs) (#250).
[x] Develop documentation for the general public (#252).
[x] utxo-db-api design document should get an editorial review (#326).
[x] utxo-db and utxo-db-api documents should be accessible somewhere (#330).
[x] ~Develop technical documentation, like ouroboros-consensus/docs/utxo-hd/report.pdf low-level report~ (superseded by haddocks documentation).

Why do we have a changelog diff anchor? Differences between volatile anchors and diff anchors.

Currently, the docs folder is structured as follow:

|-docs
  |-report
  |-website
    |-contents
      |-about-ouroboros
      |-for-developers

As mentioned above, we need some documentation for the general public and some technical documentation aimed at developers.

Documentation for the general public (in about-ouroboros): A utxo-hd.md file describing the motivation for UTxO-HD, what users can expect from using either in-memory or LMDB, configuration options, installation requirements
Documentation for developers/technical documentation (in for-developers):
- utxo-hd.md: high-level description of the feature and files structure. Maybe a section on how downstream packages are affected? (I think that's mostly having to use ledger tables and mapkinds in some places)
- utxo-hd/ : markdown files for important concepts/components.
- Design concepts (re-iterating parts of the utxo-db-api document, like the partitioned in-memory/on-disk representation)
- Ledger states with holes
  - Ledger tables
  - Hard fork combinator
- The new LedgerDB
  - BackingStore
  - Changelog
- Ledger-HD: more on-disk tables ...