Re: [bitcoin-dev] Bitcoin Core 0.12.0 release candidate 1 available

[Jonas Schnelli via bitcoin-dev]

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> Why is the minimum storage quota of 550 MiB necessary for pruning
> nodes if the block data is not served to other nodes ? Could the
> client just do transaction verification and transaction relaying
> and only keep the block(s) being verified on disk ?
> 

We try to allow reorgs ~288 blocks deep also in pruning:

- From code comments:
Require that user allocate at least 550MB for block & undo files
(blk???.dat and rev???.dat)
At 1MB per block, 288 blocks = 288MB.
Add 15% for Undo data = 331MB
Add 20% for Orphan block rate = 397MB
We want the low water mark after pruning to be at least 397 MB and
since we prune in
full block file chunks, we need the high water mark which triggers the
prune to be
one 128MB block file + added 15% undo data = 147MB greater for a total
of 545MB
Setting the target to > than 550MB will make it likely we can respect
the target.



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Re: [bitcoin-dev] Bitcoin Core 0.12.0 release candidate 1 available

[Simon Selitsky via bitcoin-dev]

>> Block data that is stored can be used by other software, or potentially be
>> served to other nodes. The latter is not implemented at the moment - it 
>> would require a change to the P2P protocol, thus right now pruning nodes 
>> don't serve block data at all.

Why is the minimum storage quota of 550 MiB necessary for pruning nodes
if the block data is not served to other nodes ? Could the client just do 
transaction verification and transaction relaying and only keep the block(s) 
being verified on disk ?


On Jan 25, 2016, at 10:05 AM, Wladimir J. van der Laan via bitcoin-dev 
 wrote:

>>> To enable block pruning set prune= on the command line or in
>>> bitcoin.conf, where N is the number of MiB to allot for raw block & undo
>>> data.
> 
>> From having read the Bitcoin whitepaper quite a few months ago ago, I have 
>> the 
>> very very basic understanding that pruning is meant to:
>> - delete old transaction data which merely "moves coins around"
>> - instead only store the "origin" (= block where coins were mined) and 
>> "current location" of the coins, i.e. the unspent transactions. Notably, I 
>> understood it as "this is as secure as storing everything, since we know 
>> where 
>> the coins were created, and where they are".
>> 
>> So from that point of view, I would assume that there is a "natural" amount 
>> of 
>> megabytes which a fully pruned blockchain consists of: It would be defined 
>> by 
>> the final amount of unspent coins.
>> I thereby am confused why it is possible to configure a number of megabytes 
>> "to allot for raw block & undo data". I would rather expect pruning just to 
>> be 
>> a boolean on/off flag, and the number of megabytes to be an automatically 
>> computed result from the natural size of the dataset.
>> And especially, I fear that I could set N too low, and as a result, it would 
>> delete "too much". I mean could this result in even security relevant 
>> transaction data being deleted?
> 
> The term 'pruning', unfortunately is very much overused and overloaded in the
> bitcoin ecosystem. Satoshi's paper refers to UTXO pruning. This is Pieter 
> Wuille's "ultraprune",
> which has been part of Bitcoin Core for more than three years.
> 
> Block pruning is not mentioned in that paper because it is just 
> administrative,
> the only reason that nodes store historical blocks at all is to serve it to 
> other nodes,
> as well as to catch up the wallet status and for -reindexes.
> 
>> Thus, it would be nice if you could yet once more edit the release notes to:
> 
> I don't have time to work on the release notes right now, but if someone else
> wants to contribute that'd be awesome.
> 
>> - explain why a N must be given
> 
> To give a quotum. The point is that the user can choose how much harddisk 
> space they want to
> dedicate to block storage.
> 
> Block data that is stored can be used by other software, or potentially be
> served to other nodes. The latter is not implemented at the moment - it would 
> require
> a change to the P2P protocol, thus right now pruning nodes don't serve block
> data at all.
> 
>> - what a "safe" value of N is. I.e. how large must N be at least to not 
>> delete 
>> security-relevant stuff?
> 
> There is no security compromise with pruning. Any value of N is intended to 
> be safe.
> 
> Very low values would delete undo data that may be necessary in a 
> reorganization,
> but this is prohibited by argument checks.
> 
> Release notes are not meant as a replacement or supplement for documentation.
> The documentation for -prune is this:
> 
>  -prune=
>   Reduce storage requirements by pruning (deleting) old blocks. This mode
>   is incompatible with -txindex and -rescan. Warning: Reverting this
>   setting requires re-downloading the entire blockchain. (default: 0 =
>   disable pruning blocks, >550 = target size in MiB to use for block
>   files)
> 
>> - maybe mention if there is a "auto" setting for N to ensure that it choses 
>> a 
>> safe value on its own?
> 
> As said, there is no safe or unsafe value. The lowest acceptable value is 
> just as safe
> as storing everything.
> 
> Wladimir
> 
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Re: [bitcoin-dev] Bitcoin Core 0.12.0 release candidate 1 available

[xor--- via bitcoin-dev]

On Monday, January 25, 2016 04:05:59 PM Wladimir J. van der Laan wrote:
> I don't have time to work on the release notes right now, but if someone
> else wants to contribute that'd be awesome.

I cooked my first pull request to resolve this:
https://github.com/bitcoin/bitcoin/pull/7416

Thanks for all the explanations you folks provided! :)


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Re: [bitcoin-dev] Bitcoin Core 0.12.0 release candidate 1 available

[Wladimir J. van der Laan via bitcoin-dev]

> 
> So I'm interested whether this limitation has been lifted, and the whole 
> feature is considered as finished.

Yes, it's exactly that limitation that has been lifted!

> If yes, I would highly recommend advertising it in the new release notes - as 
> said, the disk space reduction is a big deal.

Good idea, has been added by Marco Falke in commit fa31133,

Wladimir
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Re: [bitcoin-dev] Bitcoin Core 0.12.0 release candidate 1 available

[Wladimir J. van der Laan via bitcoin-dev]

On Sun, Jan 17, 2016 at 11:57:28PM +0100, xor--- via bitcoin-dev wrote:
> On Sunday, January 17, 2016 11:08:08 AM Wladimir J. van der Laan via bitcoin-
> dev wrote:
> > Preliminary release notes for the release can be found here:
> > 
> > https://github.com/bitcoin/bitcoin/blob/0.12/doc/release-notes.md
> 
> 
> The part which lists raw Git pull requests says:
> > #6057 ac5476e re-enable wallet in autoprune
> 
> But the main, handwritten part does not mention this.
> Is pruning really finished, i.e. could I safely use it as a wallet "end-user"?

It has been tested in git for almost half a year. This RC is the first binary
release that contains the functionality.

It is extremely unlikely that the wallet will eat your coins (always backup
nevertheless), but I can't guarantee there won't be some issue where the wallet
and chain get out of sync and you're forced to redownload the blockchain.

> IMHO it would be one of the most interesting feature for users, as it could 
> fix the issue of taking >60 GB of disk space.
> 
> So if it is finished, please mention that
> - it's finished
> - how to enable it.

How to enable it is still the same as mentioned in the 0.11 release notes:
https://github.com/bitcoin/bitcoin/blob/v0.11.0/doc/release-notes.md#block-file-pruning

Wladimir
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