Async volume upload

By default, the Archiver uploads the archive files (zips containing emails) during the archiving process. On appliances with a high daily email ingestion rate, it's possible to additionally increase archiving speed by enabling this feature. There are three volume behaviors:

• Caching write: local volume on which the archived emails are instantly stored.
• Async upload: volume on which the previously stored emails are asynchronously uploaded.
• Read only: no files will be stored in this volume, but it will be used when fetching emails.

Asynchronous archives uploads are automatically managed by the Archiver, and will be processed in a matter of minutes. When an archive has been successfully uploaded to all async volumes, it is then removed from the caching write volume. If an async volume fails to respond when attempting an upload, the archive will be uploaded on the remaining async volumes, and will not be removed from the caching write volume until it is successfully uploaded. Please make sure to not accidentally fill the local disk where the caching write volume is located, otherwise the archiving process will be suspended.