Mainnet began on block 148,888. It supports 32 GiB and 64 GiB sectors.
Calibration network is the most realistic simulation of the Filecoin mainnet:

- Prospective storage miners can experience more realistic sealing performance and hardware requirements due to the use of final proofs constructions and parameters
- Prospective storage clients can store and retrieve real data on the network. Clients can participate in deal-making workflows and storage + retrieval functionality.
- Same as mainnet, the calibration network supports 32 GiB and 64 GiB sectors.
The Nerpa network is deprecated, find more information at https://github.com/filecoin-project/community/discussions/74#discussioncomment-1348469.