From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id C479774 for ; Sun, 2 Aug 2015 22:35:54 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 20E4E7D for ; Sun, 2 Aug 2015 22:35:54 +0000 (UTC) Received: by pabkd10 with SMTP id kd10so74277928pab.2 for ; Sun, 02 Aug 2015 15:35:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=lbAe2IX+5Hr8I+iEWsQboDm7eMvJEIYAFEuRi0z/qmM=; b=sMd6zVMEwdLdR3O/Ua/ArGgLtoZyivBTog6koghj3GQsuxUK083A8zTo15OXqcv176 2o9/rFhSj4Q1eijnPFMuAyhIw4dVx2TENnyQGp1qlUh8A8B25XwqwY2j0dQw2TetrEnk UDmLVC7QgECtQG0iI1sWFOO8TygmDMH2ob7PjOaJXRrR61iOGvI25hIZ8At9D8PDj5BH uYIblDONHdHC0rSKZK2QYyA31e+L5GyhkK3S7YzlHCpDD+BO8HQQsPAxgACpcTRtBkRR HBHOBccEwv0oUXJ6XM3BF0Y8bo/etb0jv+DABj4GBQZ7DoHGpHu+bC+C73rBj7clYmTX BQzA== X-Received: by 10.66.253.170 with SMTP id ab10mr7160592pad.135.1438554953875; Sun, 02 Aug 2015 15:35:53 -0700 (PDT) Received: from erisian.com.au (116.45.96.58.static.exetel.com.au. [58.96.45.116]) by smtp.gmail.com with ESMTPSA id b4sm15246257pdn.42.2015.08.02.15.35.49 (version=TLSv1 cipher=RC4-SHA bits=128/128); Sun, 02 Aug 2015 15:35:52 -0700 (PDT) Sender: Anthony Towns Received: by erisian.com.au (sSMTP sendmail emulation); Mon, 03 Aug 2015 08:35:45 +1000 Date: Mon, 3 Aug 2015 08:35:45 +1000 From: Anthony Towns To: Gavin Andresen , bitcoin-dev@lists.linuxfoundation.org Message-ID: <20150802223545.GA14286@navy> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] Block size following technological growth X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 02 Aug 2015 22:35:54 -0000 On Thu, Jul 30, 2015 at 12:20:30PM -0400, Gavin Andresen wrote: > On Thu, Jul 30, 2015 at 10:25 AM, Pieter Wuille via bitcoin-dev > > Some things are not included yet, such as a testnet whose size runs ahead > > of the main chain, and the inclusion of Gavin's more accurate sigop > > checking after the hard fork. > First, THANK YOU for making a concrete proposal! > So we'd get to 2MB blocks in the year 2021. I think that is much too > conservative, and the most likely effect of being that conservative is that > the main blockchain becomes a settlement network, affordable only for > large-value transactions. I haven't seen anyone do the (trivial) maths on this. Have I just missed it? By my count: - blocks in 25 btc in rewards and about 0.5 btc in fees per block - at ~$300 USD per btc, that's ~$7,650 per block - current hashrate is ~400 PH/s; so ~240,000 PH/block works out to having to spend about 30PH per dollar earnt. - for comparison, https://products.butterflylabs.com/cloud-mining-contracts.html quotes $1.99 per GH/s for 12 months, which by my count is 60*60*24*365 / 1.99 GH/$ = 15.8 PH per dollar spent - hashrate growth has slowed from about x4/quarter to x2/year: sep '13: ~1PH/s dec '13: ~4PH/s mar '14: ~20PH/s jun '14: ~80PH/s sep '14: ~200PH/s aug '15: ~400PH/s - so, as far as I understand it, miners don't make absurd profits compared to capital investment and running costs - presumably, then, miners will stop mining bitcoin if the revenue/block drops significantly at some point - less miners means a lower hashrate; a lower hashrate makes 50% attacks easier, and that's a bad thing (especially if there's lots of pre-loved ASIC mining hardware available cheap on ebay or alibaba) - in about a year, the block reward halves, cutting out 12.5 btc or ~$3750 USD per block. without an increase in fees per block, miners will just get ~$3900 USD per block - the last time the reward for mining a block was under $4000 per block was around oct '13, with a hashrate of ~2PH/s - 13 btc in fees per block compared to .5 btc in fees per block is a 25x increase; which could be either an increase in fee/txn or txns/block - with ~500 bytes/transaction, that's ~2000 transactions per MB - 13 btc in fees ($3900) per block means per transaction fees of about $2 for 1MB blocks $1 for 2MB blocks 25c for 8MB blocks 10c for 20MB blocks (assuming full blocks, 500 byte txns) - comparing that to credit card or paypal fees at ~2.5% that's: $2 -> minimum transaction $80 $1 -> minimum transaction $40 25c -> minimum transaction $10 10c -> minimum transaction $4 - those numbers only depend on the USD/BTC exchange rate in so far as the more USD for a BTC, the more likely the block reward will pay for hashrate without transaction fees, even with the reward reduced to 12.5 btc/block. otherwise it's just USD/txn paying for USD/hashrate - the reference implementation fee of 0.1mBTC/kB equates to about 3c per transaction (since it rounds up). Even 10c/transaction is more than a 3x increase on that. What the above says to me is that even assuming everyone starts paying fees, the lightning network works great, and so do sidechains and whatever else, you /still/ want to up the volume of bitcoin txns by something like an order of magnitude above what's currently allowed within a year or so. Cheers, aj