One Lake cold Storage - how to activate?

Hi anto_n, 

1: It's rolled out, but not generally available. It's still in preview, which is like it being in a public beta. 

2: Once configured, you should see it in billing, but it might not be in the azure cost analytics report yet.   

3: There's no standards or best practices specific to Fabric right now, however there are general best practices. The sample given on MS Learn is: 

• After 30 days without modification, move files to the cool tier. After 90 days without modification, move files to the cold tier.
• After 30 days without being accessed, move files within a specific path to the cool tier. If a file is accessed, move it back to the hot tier.

This is currently planned for GA in Q3, however timelines can change. 

https://roadmap.fabric.microsoft.com/?product=onelake#plan-70f85dde-1a40-f111-88b4-000d3a376c0f