In disaggregated storage the address cookie currently contains:

• Page ID (8 bytes)
• LSN (8 bytes)
• Checkpoint ID (8 bytes)
• Reconciliation ID (8 bytes)
• Size (4 bytes)
• Checksum (4 bytes)

We are no longer using the Checkpoint ID and Reconciliation ID fields, so they should be removed from the address cookie.

We should also consider whether we need the size. A potential use case is as an aid in tracking the size of a BTree - specifically if we discard a page without loading it, say during a fast truncate, we will want a way to know the size of the page we are discarding.

Minimizing the size of the address cookie is important since it affects the fanout of the BTree.