Context:

Currently, the default collection interval is 5m and the retention of all resolutions in Thanos is set to 1y. The problem is that the 5m resolution is useless in this case, only adding more storage requirement (more that doubling the raw data). 
If we are consistent, we should:

• Either remove the 5m downsampling in the default configuration,
• Or remove the raw resolution (keeping it very short). But the downside is that the 5m downsampling is bigger (adding useless stats data).

But we should warn users that if they use a shorter interval, the preceding retention we decide to remove should be reset. We must define from what max interval the 5m downsampling resolution brings value (e.g. 2m).

Acceptance:

A plan is agreed on new retention defaults and the added documentation needed for the user.