Quote from: hazek on February 24, 2013, 09:26:29 AM

Quote from: solex on February 24, 2013, 06:40:51 AM

However, I have extracted the transaction counts and they average 1190 each. Looking at a bunch of blocks maxing out at 250Kb they are in the region of 600 transactions each, which is to be expected. Obviously, there is a block header overhead in all of them. But this does mean that the 1Mb blocks will be saturated when they carry about 2400 transactions. This ignores the fact that some blocks are virtually empty as a few miners seem not to care about including many transactions.

So 2400 transactions per block * 144 blocks per day = 345,600 transactions per day or Bitcoin's maximum sustained throughput is just 4 transactions per second.
This is even more anemic than the oft-quoted 7 tps!

Excellent. Someone finally quoted some real numbers instead of theoretical maximums, the picture is a bit clearer now, thanks!

Those numbers are bogus and show very little understanding on the part of solex.

The problem is apparent if you look at transaction 3e4116059a0edb1134126047d9e5ebfa1619b6180153cdc8390e6e36c375a179 from block #259156, one of the blocks in solex's analysis. That transaction has one input, and 41 outputs. Now for the purposes of determining how many transactions Bitcoin can perform per second, are you going to count it as one transaction, or more than one? solex is counting it as one.

As transactions become more expensive per byte people are going to use all sorts of techniques to make transaction size smaller. For instance you can combine transactions together with other parties; each transaction includes a 10 byte header. If you get together with 20 other people, you've saved 200 bytes and you improve your privacy because you've mixed your funds with those 20 other people.

The absolute minimum transaction size(1) is for single input single-output transactions. They are 192 bytes each, 182 if transaction combining is aggressively used. 1MiB/10minutes * 182bytes = 9.6tx/s

Big eWallets services like instawallet will be able to get much closer to that theoretical limit than other services simply because they'll have a wider range of txouts to chose from. We may even see agreements between services to use each others wallets just to optimize fees, with something like ripple used to settle imbalances periodically; if off-chain transactions become supported, it's quite possible even day-to-day users will be running software that does stuff like that automatically.

1) Minimum signed transaction that is. The technical minimum is 60 bytes, but such transactions are spendable by anyone and thus offer no security.