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The progress number is the ratio between the total number of transactions in the active (validated) chain, and the expected total number of transactions at the current point in time. The latter is estimated based on statistics that are hardcoded in the Bitcoin Core source code, and updated every major release. For example in version v0.19.0, the source code,...


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Your node will just ask its peers for blocks. It actually does the same thing it does for the initial sync. It starts with what it currently considers to be the chain tip (in initial sync, that's the genesis block). From there, it connects to other nodes and asks those nodes for more block headers starting with the block at its own chain tip. Typically, that ...


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A reindex will not redownload the block. However, after safely shutting down Bitcoin Core, you can delete the block file containing that block. When you start it again, you will need to reindex, but once it gets to the blocks that you deleted, it will redownload them.


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As you've discovered, Bitcoin Core is almost optimally non-performant on shared servers. The majority of the work done is on a single core, so measuring the total utilization of the CPU is not a good measure. Database operations are necessarily single threaded, and the majority of the work in the early parts of the chain are entirely consumed by this. ...


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