Hi, everyone. Welcome to the 2nd chapter in our Tencent Cloud practitioner course, Introduction to Cloud Virtual Machine, which is abbreviated as CVM. At the end of this chapter, you will have a better understanding of the basics of CVM, the features, advantages and use cases of CVM, and the billing plans for CVM. In this chapter, we will cover three sections CVM basics, CVM products, and billing plans for CVM. This video will cover the first section, CVM basics. Subsequent videos will cover the remaining two sections. Let's get started with section 1, CVM basics. In this video, we'll cover what is CVM, the evolution of CVM, regions and availability zones, CVM instances, CVM images, and CVM storage. What exactly is CVM? Cloud Virtual Machine is an elastically scalable computing service. CVM supports elastic computing, which allows it to scale in minutes. It also supports the flexible configuration of CPU, memory, and bandwidth with 99.95 percent availability and three cloud disc replicas. CVM features high stability and reliability. CVM can be managed simply through APIs, CLI, or the Tencent Cloud console. CVM features a secure network, thanks to VPC, ACL, and security groups. It offers comprehensive protection against various cyber attacks, providing Trojan and vulnerability detection capabilities, and protection against brute force attacks. Now, let's take a look at the evolution of CVM. There were three predecessors to CVM: virtual servers, dedicated servers, and virtual private servers. The earliest was virtual servers, where a portion of the server disk space was partitioned for the user. Then came dedicated servers, where a customer rented a dedicated server to host a website. After dedicated servers, came virtual private servers, where a single physical server hosted several virtual servers. Now we have CVM, where virtual servers are hosted on clusters. Let's move on to regions and availability zones. Regions are independent geographical areas. Tencent Cloud follows the naming convention of the coverage area, plus the name of the city where the data center is located, such as US East Virginia. However, for simplicity, regions will often be referred to by their city name, such as Virginia. Each region has multiple availability zones. In other words, each region has multiple physical data centers with independent electrical and network systems. A region may need multiple availability zones to sufficiently meet clients' demands. For example, if a region only has one availability zone when a data center becomes fully occupied, there will not be enough resources to meet clients' needs, necessitating the construction of a second availability zone. Multiple availability zones are also useful for disaster recovery. For example, if a data center of one availability zone goes down for whatever reason, Tencent Cloud will still be able to provide services to clients through another data center of another availability zone. For availability zones, Tencent Cloud follows the naming convention of the city plus the zone number. Tencent Cloud offers over 27 regions, and over 60 availability zones worldwide and counting. Tencent Cloud maintains several regions and availability zones for several reasons, including fault isolation, load balancing, high availability, and perhaps most importantly, nearby access. For example, having multiple regions in China such as Beijing, Shanghai, and Guangzhou, allows Tencent Cloud customers to reach their end-users that are spread out across China. Cloud services and private networks can communicate via the high-speed connections provided by Tencent Cloud. However, cloud load balancer does not support traffic forwarding across regions. Note that the private network interconnection illustrated above applies to the sharing of resources under the same account and not under different accounts. By default, a region cannot communicate with another region unless you use VPC peering, which customers are billed for. VPC peering enables data synchronization between VPC networks, routing traffic between different private IP addresses in peer VPC networks as if they were in the same network. To facilitate communication between availability zones within a region, you would have to set that up in Tencent Cloud's virtual private cloud settings. Similar to a personal computer, a CVM Instance includes components such as a CPU, memory, disk, network, and operating system. While personal computers usually use the Windows or Mac OS Operating Systems, CVM instances commonly use the Linux system. CVM instances follow the naming convention of the series.Model, followed by the specification number of vCPUs use, and memory size, in parentheses. You can manage instances via the console or APIs. The console is the go-to online portal for Tencent Cloud customers to view and manage their cloud services and products. APIs or application programming interfaces, are small snippets of code that you can send over the network to call infrastructure programmatically. APIs are useful because they can automate the process of calling virtual machines many times, saving labor costs and time. You can adjust the instance configuration online and restart the instance to apply any changes you make. Regarding security, CVMs support security policies, security groups, and login control. Security policies allow different virtual machines to communicate with other objects according to the rules you have set. Here, let's compare the different types of instance models, S1, S2, S3 and S4. Since all these instance types are standard instance types, the number at the end of the instance type name denotes which CPU generation the instance type uses. For example, S4 indicates that the instance uses the fourth CPU generation. Newer generations of CPUs are more power efficient than previous generations of CPUs, meaning that they can pack more power into the same amount of physical space. As a result, CVMs with newer CPU generations are more cost efficient. The same goes for memory which has several generations as well. Regarding private network bandwidth, the newer the instance model, the more data each virtual machine can transmit externally. In addition to the S1, S2, S3, and S4 instances, the S5 instance is now available for purchase on Tencent Cloud's console. An instance family is a collection of instance types with similar purposes and configurations. An instance type is a collection of instance configuration options, including the model, specifications, number of vCPUs, memory size, CPU model, private network bandwidth, throughput and supported availability zones. Now, let's look at the different features and use cases of four different instance types, standard, memory, high I/O and computational. Standard instances feature balanced computing power, memory and network capabilities and can be used for small and medium-sized web applications and databases and official company websites. Memory instances feature large memory size and can be used for memory intensive operations such as searching, computing and distributed in-memory caching. High I/O instances feature high I/O, high throughput and low latency and can be used for NoSQL databases, cluster databases and OLTP systems. Computational instances feature CPU with a high clock speed and a max price performance ratio and can be used for high traffic web servers, MMO game servers and HPC. As mentioned in the previous slide, standard instances are suitable for small and medium-sized web applications and databases. Computational instances are suitable for large game servers, ad service engines and high performance computing. Memory instances are suitable for memory-intensive operations, such as searching and computing. High I/O instances are suitable for low latency and I/O-intensive applications. Images are templates or installation disks for creating CVMs. They contain operating systems and relevant configuration information that can be copied to multiple virtual machines when creating CVMs, saving labor costs and time by automating repetitive and manual CVM creation. The functions of CVM images include batch deployment, specific software deployment and runtime environment backup. Image deployment is much more efficient than manual installation. Image deployment only takes 3-5 minutes, while manual installation takes 1-2 days. For image deployment, you can select an image and deploy it with one click, whereas for manual installation, you have to manually select and install the software and perform debugging. Regarding security, image deployment is tested and approved by Tencent Cloud, while manual installation relies on the expertise of development and deployment staff. The source of image deployment includes public images, marketplace images, custom images and shared images, while the source of manual installation is manual deployment from scratch. Unlike public images, custom images and shared images, marketplace images are pre-made images sold by vendors on Tencent Cloud marketplace. CVM storage can be differentiated by storage media, partition type and architecture. Different storage media include: Premium Cloud Storage, SSS Cloud Storage and Enhanced SSD. Premium Cloud storage is less costly than SSD Cloud storage and enhanced SSD. Premium Cloud storage is also more suitable for small and medium databases, while SSD Cloud storage and enhanced SSD are more suitable for medium and large databases. Different partition types include system disks and data disks. In a virtual machine, operating systems are installed on the system disk while data is installed on the data disk. Different architectures include: Local Disks, Cloud Block Storage and Cloud Object Storage. Cloud block storage is an abstracted version of the Cloud's hard drive or solid-state drive that you attach to the virtual machine, while Cloud object storage is a separated concept where you can store images or files without having to attach a CVM to it.