For ease of maintenance on OpenStack Object Storage, Rackspace recommends that you set up at least five nodes. Each node will be assigned its own zone (for a total of five zones), which will give you host level redundancy. This allows you to take down a single zone for maintenance and still guarantee object availability in the event that another zone fails during your maintenance.
You could keep each server in its own cabinet to achieve cabinet level isolation, but you may wish to wait until your swift service is better established before developing cabinet-level isolation. OpenStack Object Storage is flexible; if you later decide to change the isolation level, you can take down one zone at a time and move them to appropriate new homes.
