Packaging DCPs used to be a massive faff. (it might still be one)
Basically they are a tar[1] of images with a bunch of audio streams for different speaker configurations. depending on the quality settings, they can be encoded for higher colour space (ie 16 bit log per channel)
Even with lossless jpeg2000, these packages can be huge.
But, back in 2011, the biggest problem was encoding jpeg2000 required hardware to get anything near realtime performance. (I also think there were dedicated DCP packaging machines, but I never actually saw one.)
One of my colleagues decided the best way to ship the finalised movie was to open up an NFS port on sohonet and let the technicolor hook the DCP packager directly.
it worked, but our CTO diplomatically asked them to stop.
[1] not actually but conceptually similar