Whoa, whoa, wait...
From the point of view of old clients, segwit adds one coinbase output that contains the root hash of the Merkle tree that commits to the witness transaction ids. It uses 47 extra bytes per block, so technically, yes, it "wastes precious blockchain space".
So, 47 bytes per block. That's not too unreasonable. But...
This then gets us to my question that is not being answered. On average, how many bytes in the blockchain will be needed for a standard payment sent via segwit?
Is this ever less than it would be now?
Is this ever the same as it is now?
Is this usually about 50 bytes more per tx?
50 bytes per transaction for fully-validating nodes? This needs to be answered.
I would like to see an answer to this too, it seems everyone is avoiding this question. Fully validating nodes are very important for those of us that want to verify the blockchain ourselves and are required for bootstrapping new nodes.
01000000000102fff7f7881a8099afa6940d42d1e7f6362bec38171ea3edf433541db4e4ad969f0
0000000494830450221008b9d1dc26ba6a9cb62127b02742fa9d754cd3bebf337f7a55d114c8e5c
dd30be022040529b194ba3f9281a99f2b1c0a19c0489bc22ede944ccf4ecbab4cc618ef3ed01eef
fffffef51e1b804cc89d182d279655c3aa89e815b1b309fe287d9b2b55d57b90ec68a0100000000
ffffffff02202cb206000000001976a9148280b37df378db99f66f85c95a783a76ac7a6d5988ac9
093510d000000001976a9143bde42dbee7e4dbe6a21b2d50ce2f0167faa815988ac000247304402
203609e17b84f6a7d30c80bfa610b5b4542f32a8a0d5447a12fb1366d7f01cc44a0220573a954c4
518331561406f90300e8f3358f51928d43c212a8caed02de67eebee0121025476c2e83188368da1
ff3e292e7acafcdb3566bb0ad253f62fc70f07aeee635711000000
the above is from
https://github.com/bitcoin/bips/blob/master/bip-0143.mediawikiit is a 2 input 2 output tx in the witness space.
In addition to the above, the much smaller anyonecan spend tx is needed too. I think it will be about 100 bytes?
so we have a combined space of around 800 bytes against the 1000 bytes the usual 2 input/2 output tx occupies. Or was that 400 bytes that the 2input/2output tx takes?
I was told that all nodes are expected to be pruning nodes anyway, so you dont have to worry about any full node requirements. They will make sure all the archive copies will forever be kept safe and not tampered with. you can trust them. it is better for bitcoin to require trust
Isnt it nice to have all the hard choices made for you. We can trust in the math done by the central planners. Dont worry, be happy.
James