When start geth(Ethereum client) First time,showing message like "generating DAG for epoch ........." mining is taking too much to start

Question

What i have
Case 1. following command line without --dev option (take too much time to start to mining)

geth --datadir ~/privateBlockChain1 --mine --minerthreads 1 --networkid 1300 --rpcport 8000  --port 30301 --rpcapi="db,eth,net,web3,personal,admin" --rpc --maxpeers 0 --nodiscover --targetgaslimit 110000000000 console

Case 2. following command line with --dev option(using this command line argument , mining works fine)

geth --datadir ~/privateBlockChain1 --mine --minerthreads 1 --networkid 1300 --rpcport 8000  --port 30301 --rpcapi="db,eth,net,web3,personal,admin" --rpc --maxpeers 0 --nodiscover --targetgaslimit 110000000000 **--dev** console

Scenario

1. Start geth by case 1 command. Step 2.
2. suppose block created by case 1 command as for example -> #34544 block
3. Start geth by case 2 command
4. Block start creating from #1 block , it is not resume from #34544 block, how to fix it.

What i want?

a) how to mining start quickly(with in a second or a minute) when i start geth command line
b) if i do'nt want to use --dev option , then how can start mining fast?
c) suppose if you say, --dev is only option to start mining fast in startup, then how can i resume mine block from previous(i.e #34544 not from #1 block)
d) what is the advantage and disadvantage of --dev option with geth.

Answer 1

Looking at the source code the --dev option appears to only turn off networking. No listening, no discovery of other nodes. So I don't immediately assume you can't use the --networkid option as well.

I am seeing a lot of talk about how the --dev flag prevents you from being a part of a test network(including the private network you setup). However, I have not been able to corroborate this within the source code within my 15 minutes of research. If I find out definitively, I'll update my answer.

Assuming that's true, the --dev flag will always create a standalone network and always start at block #1. So I guess my advice is to not use --dev if you don't want to start from scratch every time.