BLZG-1003 (Support larger metabit allocations) introduced demi-spaces near the head of the RWStore that come into play once the backing store has a large number of allocations. It appears that the demi-space model requires additional isolation in order to have a deterministic snapshot of these demi-spaces. The absence of that isolation can result in errors in the RWStore VERSION (stored in the metabits header) or in the allocators (such as two allocators at the same address) if the RWStore roles through a commit during the snapshot.
We should also implement a utility class to validate snapshots and HALog files. This could be essentially the same as the HARestore, perhaps with an open to test-open the Journal (perhaps in a read-only mode) after decompressing each snapshot and after applying each HALog file. There might be some additional tests that we could apply once we open that journal. If we are just running validation then the journal should be deleted afterwards.