Block archiving

The high throughput of Klaytn should result in high storage costs. Klaytn plans to perform block-archiving to ease storage burdens of participating nodes. With block archiving enabled, ENs may remove bodies of stale blocks, maintaining only a certain number of the last blocks. Only a subgroup of Klaytn network nodes will keep all the blocks in cost-effective storage and they will serve read requests by verifying older transactions no longer stored in ENs. However, even block archiving ENs will still have to keep the headers from all archived blocks in order to allow clients to securely verify the contents of the archived blocks.

This process can effectively reduce the storage cost of ENs, encouraging diverse participants to join the ENN. Assuming 100 TPS in average and 1-second block latency, the size of data that an EN must replicate can be significant. If the average transaction size is 300 bytes, the expected EN daily storage requirement is 2.5 GB/day (=300x100x86400). While this does not hinder servers and desktops (where storage space is more easily expandable and less expensive), certain ENs running their nodes on lighter machines such as laptops could find this storage requirement a burden. By allowing ENs to only keep a fixed number of blocks, block archiving will extend its benefits to a broad spectrum of audiences on the network, fortifying data redundancy and security without requiring ENs to replicate an ever-growing ledger of blocks.

Whereas removing block bodies may be perceived as weakening decentralization as block archiving nodes cannot independently verify all historical transactions without the help of other nodes. Nonetheless, not all applications need constant access to the complete history of transactions, and we believe that block archiving is a welcome feature strongly preferred by certain groups of services --- services that require only the latest states of applications. Serving all blocks in this context is inefficient and less desirable. We believe that block archiving will benefit many applications requiring high replication levels and the security of blockchain technology.