The mail host is ext4 (John, 2026-09-19). There is no filesystem snapshot
to take, so the sequence as written puts the whole store inside the
downtime: stop, copy everything, start.
An rsync before the stop and a second one after it moves the bulk while
mail is still flowing and leaves only the delta in the window. The first
pass is knowingly inconsistent and exists only as a warm-up; the second,
once the process has actually exited, is what makes the copy consistent.
A RocksDB store suits this, being mostly immutable SST files: what changes
between the passes is the WAL, the MANIFEST and any compaction output.
Step 3 now says so, and says to time both during the rehearsal, because
the second pass is the window and nobody knows yet how long it is.
jcoffey-dev
7c27bae4f3