ACA-Cloud1 Exam Dumps : ACA Cloud Computing Associate

According to the Alibaba Cloud Academy, Auto Scaling is a service that automatically creates and releases ECS instances based on pre-defined rules in order to scale services to match demand. Furthermore, it can configure server load balancer and relational database service white lists, without any manual intervention. Therefore, using Auto Scaling is the most preferred method from the perspective of cost and implementation simplicity, as it can dynamically adjust the number of ECS instances according to the traffic fluctuations, without requiring manual operations or wasting resources. The other methods are either too complex, inefficient, or costly to implement. References: Introduction to Alibaba Auto Scaling - Cloud Academy, ACA Cloud Computing Exam Preparation Course - Alibaba Cloud, Module 4: Cloud Computing Elasticity, Lesson 1: Auto Scaling, Slide 2.

 A is the correct answer because RDS provides whitelist access policies that allow you to set permitted IP addresses and IP network segments to effectively prevent hackers from attacking the server by port scanning. A whitelist is a security feature that specifies the IP addresses or CIDR blocks that are allowed to access your RDS instance. By default, the whitelist is empty, which means that no IP address can access your RDS instance. You can add IP addresses or CIDR blocks to the whitelist according to your business needs. You can also create multiple whitelist groups and assign different IP addresses or CIDR blocks to each group. This can help you manage the access permissions of different users or applications12

References: 1: Configure a whitelist 2: ApsaraDB RDS:Configure an IP address whitelist

 = A is the correct answer because the memory size of an ECS instance is determined by the instance type, and it cannot be changed independently. If you want to change the memory size of an ECS instance, you must change the instance type to another one that has a different memory size12

B, C, and D are incorrect answers because the system disk size, data disk size, and number of data disks of an ECS instance can be changed without changing the instance type. You can use the ECS console or API to resize the system disk or data disks of an ECS instance, or add or remove data disks from an ECS instance3456

References: 1: Overview of instance families 2: Change the instance type 3: Resize disks 4: Resize a disk 5: Attach or detach data disks 6: Attach or detach a data disk