Hi Quách Thu, I'm not sure what you mean about site mining, as I understand you referred about cloud mining. I would not recommend you purchase any cloud mining service. If service providers get profit, you will get not much, but if they get loss, you must pay a lot. This time is a hard time for gpu mining, if you could handle and have some spare money, you may think about purchasing some asic miners to mine BTC (as you mentioned you like mining BTC). By the way, please note that asic miners are very noisy (typically 75dB), and hot.