Archive Compression $ DeDupe

DVS files are compressed by default except when they become a certain size and they become DVF files
Items going in to CAB files are not compressed, because it slows things down and typically when you compress a file already compress, it makes the CAB file bigger

EV does not do block level deduplication. Instead it hashes the attachments before it turns in to a DVSSP, if the hash is not found within the Fingerprint database, then a new DVSSP file is made, if the hash IS found, then a pointer to the file in the database is made and the same item won't be stored

This is different to how it works if you have a device that does compression and deduplication, then EV will simply let the device handle it