It seems that people are always keen to discuss cloud computing, and all the questions about cloud computing are also of concern. Among the major enterprises, they often encounter some very common problems, which can be roughly divided into several broad categories, such as reliability, system performance and system expansion, system security and cost issues. Reliability issues There are many root causes for reliability problems such as overload, code problems, server crashes, database problems, bandwidth, hardware, cloud issues, CDNs, data center issues, and more. In the long run, our biggest and most frequently encountered problem is disk space. The number of customers surged and the number of blogs surged. No matter how much disk space you provide, they run out of disk space to handle data and other transactions. So, like other system administrators, we do our best and do everything we can to increase the disk size and storage space. Database problems are another common problem. From overload to common replication issues. Clients often misunderstand duplication, do not understand the need for duplication and duplication, so they often cause problems, and we continue to address these issues, including the use of new detection, monitoring and management tools to keep our systems up and running, ensuring data accuracy. This work has become increasingly important as data in electronic become increasingly critical business and the advertising industry, more and more financial-oriented. Other reliability issues include PHP, Java and other Django issues, of course, including the collapse of the system and our daily monitoring, management and resolution issues. System performance and scalability issues System performance issues include overloading, which is a common CPU, RAM and IO are heavily occupied; many users (sometimes the same day at the same time) login to the customer site posed a variety of problems. It is unpredictable and unpredictable that system expansion problems are different from other issues in the boundless Internet world. In order to cope with the growth of the business in the coming days, weeks and even months, the system needs to be rapidly established or expanded More needs to be said. This is usually not the case with system architectures, with poor load balancing, or even no load balancing, or with no portable PHP / Java sessions. System security issues System security has always been a major issue. Although our system is generally safe, our clients are using insecure code and additional tools such as Cpanel or various management interfaces such as PHPMyAdmin are not secure. Therefore, we are not careful, these bad guys have a chance, but fortunately, our security is multi-level, and the distribution of the authority is the lowest, so less destructive to the system security. However, occasionally there will be system damage, we have to clean up the system, change the authorization, add customer logs and security monitors, and so on. Occasionally, we also audit to see if there is a hacker and its hiding place. Cost problem How to save money seems to be compulsory for every business. This is not a technical problem, but we often find that customers spend a lot of system and server costs, or even spend too much money wasted. They do not know how to solve or debug the system because they are slow, or they buy a lot of servers though they do not know how to virtualize and put them in a private cloud, although they have a lot of functionality. By debugging your system, you can scale it up without having to purchase a new system or expand your system with a more cost-effective way to create private clouds, saving you a lot of money.