I just did a very rough calculation on my development build and came up with about 5% overhead each for the database and index. So expect to use about an extra 10% of disk on top of the message blob size.
If disk space is a concern, there's also an option you can set with zmvolume to compress message blobs stored on a given volume. This will allow you to use less disk space for the message store, at the expence of some extra CPU load. |