Quote from: satoshi on November 25, 2010, 05:51:39 PM

It's not the downloading that takes the time, it's verifying and indexing it.

This is not true of many novice users, who say things like "well it took several hours to catch all the 90 000 blocks but finally it arrived" (quoted from one new user, on IRC, today).

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Bandwidthwise, it's more efficient than if you downloaded an archive.

Agreed. Compressed in an archive, blk0001.dat is around 36MB.

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Bitcoin only downloads the data in blk0001.dat, which is currently 55MB, and builds blkindex.dat itself, which is 47MB. Building blkindex.dat is what causes all the disk activity.

During the block download, it only flushes the database to disk every 500 blocks. You may see the block count pause at ??499 and ??999. That's when it's flushing.

It remains the download, not the verification, that has the highest variability of experience, where first time users see a delay of 30 minutes to several hours before the software is actually usable. Some P2P nodes may be extremely slow (I see high variability in latency and throughput for old blocks, and blocks larger than 512 bytes). End user bandwidth may be low, spotty or expensive. Firewalls are often a problem.

I'm betting that the above complaint from a new user was due to a Microsoft firewall; but the point stands: large variance of network configuration and capability implies the P2P download impact may be far, far greater than impact of on-disk verification of 90,000 blocks.

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Doing your own verifying and indexing is the only way to be sure your index data is secure. If you copy blk0001.dat and blkindex.dat from an untrusted source, there's no way to know if you can trust all the contents in them.

Who said untrusted? The proposal is that you distribute blk0001.dat (and only blk0001.dat) in the bitcoin.org official client downloads. And of course the client will spend some time verifying blk0001.dat upon first use. This is unavoidable, and nobody has proposed changing or eliminating verification.

Just shipping blk0001.dat with official bitcoin would eliminate several headaches that new bitcoin users continue to experience.