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- can keep wallet file as cold storage (keep my money safe)
con :
- need actually 55Go to store
- need 2-4ko/s of Upload
- need to trust the "PC" ... system operator
Not really. Electrum provides a much better interface for cold storage spending compared to Bitcoin Core.
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- need 2-4ko/s of Upload
Unless you are opening port 8333, upload speed does not matter much. Download speeds matter much more.
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I would urge anyone thinking about doing this to think twice. The bootstrap.dat linked from the website could actually be some kind of attack, although I don't know exactly how the file gets used so I can't tell you what the vector might be.
Anyway, since 0.10, the bootstrap.dat method is basically obsolete. It is not faster than downloading directly over the Bitcoin network, so it serves no purpose.
Unless you end up getting an .exe file, it is not much of a risk. Bitcoin automatically verifies each block to ensure that it is valid.
Headers-first synchronization allows the client to download from various sources and verifies simultaneously.
Here is a list of (mostly failed) combinations:
bitcoin-qt 0.9.6
512MB single core 1.6GHz AMD - forget it
1024MB quad core 1GHz raspberry pi - forget it. burned out a 64GB usb stick with too many rw before it had reindexed the blockchain
2048MB duel core 1.9GHz Dell - OK
6.2GB quad core 3.1 GHz Intel - OK, except that 0.9.6 is now obselete
bitcoin-qt 0.11.0
6.2GB quad core 3.1 GHz Intel - presently reindexing the blockchain (since 25th November)
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Comparing clock speeds makes not much sense. The IPC matters much more, an AMD FX6300 won't win a I7 4790K even with higher clock speed.
1024MB quad core 1GHz raspberry pi - forget it. burned out a 64GB usb stick with too many rw before it had reindexed the blockchain
You probably don't need to reindex that often. You can easily just copy the entire data directory from another computer so that it won't have to verify the blocks again. If you have a spare HDD lying around, that's even better, just plug it in.