My goal is to be able to access my Mist Wallet on my iMac (which I installed 8 months ago, and bought some Ether on then). I deleted my Blockchain and ran Geth through the Terminal, with this: ./geth --fast --cache 1024
However, it stopped the Fast Sync at 2.4 million blocks. And then went very slow (to my calculations: 41 days until all of the blockchain has been downloaded.
What is the solution do getting access to my Mist wallet faster?
The Ethereum Blockchain was attacked using a computational Denial-of-Service attack. This affects blocks 2.4 million to 2.7 million.
Today the network was attacked by a transaction spam attack that repeatedly called the EXTCODESIZE opcode, thereby creating blocks that take up to ~20-60 seconds to validate due to the ~50,000 disk fetches needed to process the transaction.
If you're using geth, use the options --cache 1024 --targetgaslimit 1500000 --gasprice 20000000000, if you're using parity, use the options --cache-size-db 1024 --gas-floor-target 1500000 --gasprice 20000000000 --gas-cap 1500000, which will increase processing speed.
For Hyperledger Besu its --target-gas-limit=1500000 --min-gas-price=20000000000
For more info, see this post on the Ethereum Blog
Alternatively you could use a light sync, which only validates new blocks. Use geth --light. Now, geth --fast --cache=1024 should be sufficient as there are more than the 1024 blocks after the affected blocks which are validated on the fast sync.
