Failure Modes, Recovery, and Trust¶

Page Maps¶

graph LR
  family["Reproducible Research"]
  program["Deep Dive DVC"]
  section["Data Identity Content Addressing"]
  page["Failure Modes, Recovery, and Trust"]
  capstone["Capstone evidence"]

  family --> program --> section --> page
  page -.applies in.-> capstone

flowchart LR
  orient["Orient on the page map"] --> read["Read the main claim and examples"]
  read --> inspect["Inspect the related code, proof, or capstone surface"]
  inspect --> verify["Run or review the verification path"]
  verify --> apply["Apply the idea back to the module and capstone"]

Identity matters because failure eventually arrives.

Module 02 is not finished when you can explain hashes in the abstract. It is finished when you can explain what a broken recovery or identity story actually means.

What good recovery is proving¶

When a DVC repository restores tracked content after loss, it is proving something narrow but important:

the tracked identity was recorded
the durable storage layer still has the content
the workspace can be rebuilt from that recorded state

That is a strong claim.

It is not the same as proving every part of the project is correct or complete.

Common failure questions¶

When recovery or identity seems broken, ask:

which layer is missing or inconsistent
whether the content identity was recorded but not stored durably
whether the workspace is out of sync with recorded state
whether a published artifact is being confused with full repository state

This keeps the diagnosis grounded.

A practical failure table¶

Symptom	Likely meaning
tracked file is missing after checkout	cache may not contain the needed content
`pull` cannot restore an object	remote durability is incomplete or misconfigured
local file exists but hash or identity does not match expectations	workspace drift or external modification occurred
published bundle exists but full repository state cannot be rebuilt	published trust and recovery durability are being confused

These are not random operational annoyances. They are boundary clues.

A small recovery picture¶

flowchart LR
  loss["local loss"] --> remote["remote still has tracked content"]
  remote --> pull["dvc pull restores cache"]
  pull --> checkout["dvc checkout rebuilds workspace"]
  checkout --> verify["verify what was restored and what was not"]

The last step matters just as much as the restoration commands.

Why verification still matters after recovery¶

A restored file in the workspace is not automatically the whole trust story.

You still need to ask:

did we restore the tracked content we expected
what layer is authoritative for that claim
is the published contract still valid after restore

This is why the capstone's recovery route includes review artifacts and not only commands.

A small example¶

Suppose you delete local tracked data and then use the remote-backed recovery route.

Strong explanation:

the repository restored the tracked content from remote to cache and rebuilt the workspace from that content. This proves the durable recovery path for tracked artifacts is working.

Too-strong explanation:

everything about the project is now fully recovered.

The second statement overreaches. Recovery is powerful, but it still has a scope.

Two confusions to avoid¶

Confusing published release state with full recovery state¶

publish/v1/ may be enough for downstream trust, but it is not the full internal repository state. A published bundle can remain valid while broader repository recovery is still a separate question.

Confusing local convenience with durable truth¶

If a file still happens to exist on disk, that does not prove the remote story is sound.

Recovery discipline is about surviving loss, not merely about noticing that the workspace is currently populated.

What a healthy recovery review sounds like¶

Good review language sounds like this:

The remote-backed recovery route successfully restored tracked content and allowed the workspace to be rebuilt. The publish bundle also verified after restore. This proves the tracked artifact durability story is working for those surfaces.

That sentence is strong because it says what was proven and stops there.

Keep this standard¶

Whenever a recovery story sounds vague, ask:

what exactly was restored
from which layer
into which layer
what evidence confirms the result

Those questions keep Module 02 grounded in trust rather than in command mythology.