I suppose this begs two questions: 1) why not have a partial archive store the most recent X% of the blockchain by default? 2) why not include some sort of torrent in QT, to mitigate this risk? I don't think this is necessarily a good idea, but I'd like to hear the reasoning. On May 12, 2015 4:11 PM, "Jeff Garzik" wrote: > True. Part of the issue rests on the block sync horizon/cliff. There is > a value X which is the average number of blocks the 90th percentile of > nodes need in order to sync. It is sufficient for the [semi-]pruned nodes > to keep X blocks, after which nodes must fall back to archive nodes for > older data. > > There is simply far, far more demand for recent blocks, and the demand for > old blocks very rapidly falls off. > > There was even a more radical suggestion years ago - refuse to sync if too > old (>2 weeks?), and force the user to download ancient data via torrent. > > > > On Tue, May 12, 2015 at 1:02 PM, Gregory Maxwell > wrote: > >> On Tue, May 12, 2015 at 7:38 PM, Jeff Garzik wrote: >> > One general problem is that security is weakened when an attacker can >> DoS a >> > small part of the chain by DoS'ing a small number of nodes - yet the >> impact >> > is a network-wide DoS because nobody can complete a sync. >> >> It might be more interesting to think of that attack as a bandwidth >> exhaustion DOS attack on the archive nodes... if you can't get a copy >> without them, thats where you'll go. >> >> So the question arises: does the option make some nodes that would >> have been archive not be? Probably some-- but would it do so much that >> it would offset the gain of additional copies of the data when those >> attacks are not going no. I suspect not. >> >> It's also useful to give people incremental ways to participate even >> when they can't swollow the whole pill; or choose to provide the >> resource thats cheap for them to provide. In particular, if there is >> only two kinds of full nodes-- archive and pruned; then the archive >> nodes take both a huge disk and bandwidth cost; where as if there are >> fractional then archives take low(er) bandwidth unless the fractionals >> get DOS attacked. >> > > > > -- > Jeff Garzik > Bitcoin core developer and open source evangelist > BitPay, Inc. https://bitpay.com/ >