[CONTENT IMPROVEMENT] Pinning

[Mr0grog]

At the Berlin developer summit, we decided pinning was important to write a concept doc about.

Here was the original draft:

Pinning

IPFS nodes treat the data they store like a cache: in theory it could be thrown out at any time and re-retrieved from another node. “Pinning” a CID tells IPFS never to throw out the data associated with that CID — mainly, that means it sicks around after running garbage collection.

Some concerns:

• Note that ipfs add <filename> automatically pins, while other commands do not.
• Note that GC is not automatic?
• Should this talk about future plans around named pins and/or MFS-based pins? (Too speculative, but it should cover MFS “best effort” pinning.)
• Should this talk about pinning services?
• Would it be helpful to discuss how you might load some content through the public gateway, but then not be able to do so again a few hours later as an example?

/cc @Stebalien @hsanjuan who were also in this session

This is a subtask of #56.

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Concept docs are concise, high-level descriptions of various core concepts in IPFS. They live in the content/guides/concepts folder and should strive to answer:

1. What is this?
2. How does it relate to the rest of IPFS?
3. How can (or should?) you use it? (Note: sometimes the answer is that you should understand it, but not use it. Bitswap is probably a good example.)
4. Where do you go to learn more?
5. What is the current state of affairs?

[hsanjuan]

LGTM

[Mr0grog]

@rjharmon made major improvements in #105. I think we still want to make another pass to address the items about examples with the public gateway and how MFS is like pinning (it’s “best effort” pinned: GC determines MFS attachment by walking down from files in MFS, but if a block in the middle of your tree gets deleted with ipfs block rm, that can orphan all the child nodes and they might get garbage collected because they are technically no longer attached to your MFS).

[jessicaschilling]

Closing this issue, since substantial edits have been made in the interim - see https://github.com/ipfs/ipfs-docs-v2/edit/master/docs/concepts/persistence.md .