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diff --git a/doc/release-notes.md b/doc/release-notes.md index 0617f0a257..c5e41dfc66 100644 --- a/doc/release-notes.md +++ b/doc/release-notes.md @@ -1,6 +1,73 @@ (note: this is a temporary file, to be added-to by anybody, and moved to release-notes at release time) +Notable changes +=============== + +Block file pruning +---------------------- + +This release supports running a fully validating node without maintaining a copy +of the raw block and undo data on disk. To recap, there are four types of data +related to the blockchain in the bitcoin system: the raw blocks as received over +the network (blk???.dat), the undo data (rev???.dat), the block index and the +UTXO set (both LevelDB databases). The databases are built from the raw data. + +Block pruning allows Bitcoin Core to delete the raw block and undo data once +it's been validated and used to build the databases. At that point, the raw data +is used only to relay blocks to other nodes, to handle reorganizations, to look +up old transactions (if -txindex is enabled or via the RPC/REST interfaces), or +for rescanning the wallet. The block index continues to hold the metadata about +all blocks in the blockchain. + +The user specifies how much space to allot for block & undo files. The minimum +allowed is 550MB. Note that this is in addition to whatever is required for the +block index and UTXO databases. The minimum was chosen so that Bitcoin Core will +be able to maintain at least 288 blocks on disk (two days worth of blocks at 10 +minutes per block). In rare instances it is possible that the amount of space +used will exceed the pruning target in order to keep the required last 288 +blocks on disk. + +Block pruning works during initial sync in the same way as during steady state, +by deleting block files "as you go" whenever disk space is allocated. Thus, if +the user specifies 550MB, once that level is reached the program will begin +deleting the oldest block and undo files, while continuing to download the +blockchain. + +For now, block pruning disables block relay. In the future, nodes with block +pruning will at a minimum relay "new" blocks, meaning blocks that extend their +active chain. + +Block pruning is currently incompatible with running a wallet due to the fact +that block data is used for rescanning the wallet and importing keys or +addresses (which require a rescan.) However, running the wallet with block +pruning will be supported in the near future, subject to those limitations. + +Block pruning is also incompatible with -txindex and will automatically disable +it. + +Once you have pruned blocks, going back to unpruned state requires +re-downloading the entire blockchain. To do this, re-start the node with +-reindex. Note also that any problem that would cause a user to reindex (e.g., +disk corruption) will cause a pruned node to redownload the entire blockchain. +Finally, note that when a pruned node reindexes, it will delete any blk???.dat +and rev???.dat files in the data directory prior to restarting the download. + +To enable block pruning on the command line: + +- `-prune=N`: where N is the number of MB to allot for raw block & undo data. + +Modified RPC calls: + +- `getblockchaininfo` now includes whether we are in pruned mode or not. +- `getblock` will check if the block's data has been pruned and if so, return an +error. +- `getrawtransaction` will no longer be able to locate a transaction that has a +UTXO but where its block file has been pruned. + +Pruning is disabled by default. + + 0.11.0 Change log ================= |