How is the ledger stored on every node? I read different sourcing claiming the size of the blockchain for bitcoin. 

Some says it's 8GB, some a 100GB and some 800GB.

Now I'm wondering do all the miners computers (nodes) have to store it all ? In case it's a TB it seems like a lot. Even though it's not it's still growing everyday, so is the blockchain really entierely stored on each nodes ?

Note : I used to mine a few years back I don't remember having my storage taken up by the blockchain.
Yes. The blockchain is stored completely on a full node (unless running in pruned mode) , there are mechanisms to prune and only keep relevant data, however pruning also requires you first get the complete blockchain. The size is approx 120 GB as of now. The blockchain is growing every day (rather every 10 mins).

Miners most probably have custom solutions to compute next block , so each pool node may or may not require the full chain.