Advisory and FAQs: Raising the hard cap setting in Bitcoin SV Node software in anticipation of multi-gigabyte blocks

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The first week of August 2021 has been a record-breaking one for the Bitcoin SV (BSV) network, with a succession of three 1 gigabyte (GB) blocks mined on August 6 and 7. This shows Bitcoin can scale as always intended and that BSV can power enterprise, high volume consumer and government applications.

All three of these 1 GB blocks earned the winning miner 5 BSV coins in transaction fees, in addition to the 6.25 fixed subsidy amount per block – for a total block reward of over 11.25 coins (an 80% increase above the 6.25 coins). The substantial proportion of transaction fees generated by the record blocks reflects a trend that is important for the Bitcoin mining and transaction processing sector to remain profitable in the future. 

As demand for capacity on the mainnet continues to grow, miners representing the majority of the current hash rate on the network have signalled that they intend to raise the block size ‘hard cap’ setting on their node to 2 GB, with this change to be actioned by Friday August 13, 2021 at 13:00 (UTC).

Bitcoin Association has advised all other known miners to raise their excessiveblocksize (hard cap) setting to 2 GB in order to follow the BSV chain and avoid being forked off the network; these other known miners responded quickly, and most (if not all) known miners are expected to lift their hard cap setting to 2 GB as recommended.

Bitcoin Association is also recommending that all non-miners running the Bitcoin SV node software (exchanges, applications and others) raise their excessiveblocksize (hard cap) setting to 10 GB, and that you take this action before Friday August 13, 2021 at 13:00 UTC.

Answers to the most frequently asked questions follow. If you have any further questions, please email [email protected].

MINERS

Q: I run an instance of the Bitcoin SV Node software and am a miner on the network, what is the recommended hard cap setting for my node?

Bitcoin SV does not have a hardcoded block capsize. Each node operator is required to choose this limit before the node will start up. Most miners have chosen to use the values recommended by Bitcoin Association which is 1GB or 1,000,000,000.

Bitcoin Association is at this time recommending that all miners on the network raise the excessiveblocksize (hard cap) setting on their node software to 2 GB or 2,000,000,000. This will enable your node to accept these larger blocks from other miners and ensure that your mining node continues to operate on the network.

To permanently update your node with new settings, edit the bitcoin.conf file and add/change lines for blockmaxsize and excessiveblocksize. For example, to set the excessiveblocksize (hard cap) to 2 GB:

excessiveblocksize=2000000000

These settings will take effect the next time your node is restarted.

The relevant node settings can be updated directly without restarting the node using the setblockmaxsize and setexcessiveblock RPC calls; however the bitcoin.conf file must still be updated as otherwise the new settings will be lost when the node next restarts.

Q: Why does Bitcoin Association recommend that I raise that hard cap setting on my node?

In the short term, it is evident that there is demand for bigger blocks and higher data capacity than currently available on the Bitcoin SV network. Raising the hard cap setting to the recommended 2 GB ensures that your node will continue to follow the longest chain and accept the larger blocks being produced on the network; eliminating the risk of being forked from the network.

In the long term, this is a key step towards a future for Bitcoin in which transactions fees are the primary contributor to the viability of the network. With the fixed subsidy amount per block halved approximately every four years (in the block reward halving events), miners must earn more in transaction fees to compensate for the increasingly lower fixed subsidy portion of the block reward. This is only possible through scaling the network with bigger blocks that hold more transactions and data, all while maintaining low transaction fees to facilitate genuine utility. This is how Satoshi Nakamoto designed Bitcoin to remain profitable for miners as they gradually shift to become transaction processors, and this is the path BSV is taking to fulfill the “Satoshi Vision.”

Q: What will happen if I do not raise the hard cap setting on my mining Bitcoin SV node?

Miners who remain with a hard cap setting below 2 GB are likely to be forked off the network when a block larger than 1 GB is mined, as their node will consider bigger blocks invalid and therefore will no longer follow the longest chain.

Q: As a mining node operator, if I raise the hard cap setting on my Bitcoin SV node, will my node attempt to produce blocks of that size?

No, raising the excessiveblocksize or hard cap setting on your node does not mean that your node will attempt to produce blocks of this size, rather, this is the largest-sized block that your node will accept from another miner.

The maximum sized block that your node will attempt to produce is determined using the blockmaxsize or soft cap setting. There is no need to change this setting unless the mining pool wishes to; however, doing so will maximise the potential rewards the mining pool will receive when mining larger blocks. Bitcoin Association recommends that miners wishing to attempt to produce blocks larger than 1 GB do not adjust this limit until after August 13, 2021.

NON-MINERS

Q: I run an instance of the Bitcoin SV Node software but am not a miner on the network. What is the recommended hard cap setting for my node?

If you are running the Bitcoin SV Node software but are NOT mining, you have likely accepted a prior recommendation to set the hard cap setting on your node to 2,000,000,000 bytes. In preparation for anticipated future soft cap increases by miners, Bitcoin Association recommends increasing your hard cap to 10 GB or 10,000,000,000 bytes at this time.

Q: Why does Bitcoin Association recommend that non-mining nodes run a higher hard cap setting than on mining nodes?

We expect usage of the BSV network will continue to grow. To meet demand for more capacity, at any time, miners may continue increasing their soft cap settings to higher than 2GB (the previously recommended hard cap setting for non-miners). For non-miners, raising your hard cap limit now to 10GB ensures that your node is prepared for any future rises in block sizes produced by miners and that you will continue to follow the correct chain as block sizes grow.

If you do not wish to raise your hard cap to 10GB, you could choose any other number as long as it is equal or greater than 2 GB (2,000,000,000 bytes). However, you would need to monitor miner activity more closely to determine if you need to increase your settings again if miners begin mining blocks bigger than your hard cap setting. That is why we recommend 10GB as your hard cap setting, to allow significant room for growth before you need to again chain settings.

In the future, if miners ever prepare to mine blocks bigger than 10GB, we would advise you at such time to raise your hard cap setting to an even higher number.

Q: How do I update the configuration of my non-mining node to reflect the recommended new 10 GB hard cap setting?

To permanently update your node with new settings, edit the bitcoin.conf file and add/change lines for blockmaxsize and excessiveblocksize. For example, to set the excessiveblocksize (hard cap) to 10 GB:

excessiveblocksize=10000000000

 These settings will take effect the next time your node is restarted.

The relevant node settings can be updated directly without restarting the node using the setblockmaxsize and setexcessiveblock RPC calls; however, the bitcoin.conf file must still be updated as otherwise the new settings will be lost when the node next restarts.

Q: When does Bitcoin Association recommend that I make these changes to my non-mining node?

Bitcoin Association recommends that non-mining node operators update the appropriate settings on their node no later than 13:00 (UTC) on August 13, 2021.