Alibaba ACA-Cloud1 ACA Cloud Computing Associate Exam Practice Test

Answer : A, B, C, D

A, B, C, and D are the correct answers according to the ACA Cloud Computing by Alibaba Cloud Academy Reference Materials and documents.Comprehensive and Detailed = A, B, C, and D are the correct answers because ECS is a highly flexible service that can be used independently as a simple web server, or used with other Alibaba Cloud products, such as OSS and CDN, to provide advanced solutions. ECS can be used in applications such as:

Official corporate websites: ECS can host official corporate websites that require high performance, stability, reliability, and scalability. ECS can also support various web frameworks and languages, such as PHP, Java, Node.js, Python, and Ruby.ECS can also be integrated with other Alibaba Cloud products, such as SLB, CDN, and WAF, to improve the security, availability, and performance of the websites1

Large-traffic apps: ECS can handle large-traffic apps that require high concurrency, low latency, and high throughput. ECS can also scale up or down based on the real-time traffic demands, and use Auto Scaling to automate the scaling process.ECS can also leverage the Alibaba Cloud network infrastructure, such as VPC, Express Connect, and Global Accelerator, to optimize the network connectivity and performance of the apps2

Databases: ECS can run various database systems, such as MySQL, PostgreSQL, MongoDB, and Redis, to provide data storage and processing capabilities for different applications. ECS can also use cloud disks or local disks as the storage media for the databases, and choose different disk types, such as SSD, ESSD, and Ultra Disk, based on the performance and cost requirements.ECS can also use RDS or PolarDB to replace the self-managed databases, and enjoy the benefits of managed database services, such as backup, recovery, monitoring, and maintenance3

Simple web applications: ECS can run simple web applications that do not require complex architectures or high availability. ECS can provide fast memory and the latest CPUs to power the web applications and achieve faster results with low latency. ECS can also use OSS to store static files, such as images, videos, and documents, and reduce the storage cost and load of the ECS instances.

E is an incorrect answer because ECS is not a storage service that provides unlimited online storage. ECS is a compute service that provides virtual machines with limited storage capacity. ECS can use OSS or NAS to expand the storage capacity, but these are separate storage services that have their own pricing and billing methods.

Answer : D

D is the correct answer because OSS supports 3 internal data copies, no human intervention is required to recover the data when anything goes wrong. OSS provides high data reliability and durability by storing multiple replicas of data on different devices in the same region. OSS automatically detects and repairs data errors or failures, and ensures data consistency across all replicas.OSS also supports cross-region replication (CRR) to back up data to another region for disaster recovery12

A, B, and C are incorrect answers because they do not reflect the actual backup technology and policies of OSS.

A is incorrect because OSS does not require manual recovery of data, as it automatically handles data errors or failures.

B is incorrect because OSS provides data protection and backup for customers, and customers do not need to safeguard their own data or use offsite backups.

C is incorrect because OSS does not use RAID0+1 configuration of its underlying physical hard disks, but rather uses a distributed storage system that stores multiple replicas of data on different devices.

Answer : A

Session persistence feature in Server Load Balancer means that it can forward the access requests from a single user to the same ECS instance within a certain period to ensure session continuity. This feature is useful for applications that require users to maintain a stateful connection with the backend servers, such as online shopping or banking. Session persistence can be enabled by configuring a cookie timeout period or a source IP hash method in the Server Load Balancer console.Reference:ACA Cloud Computing Certification - Alibaba Cloud Academy,Server Load Balancer - Alibaba Cloud Academy, Session Persistence - Alibaba Cloud Documentation Center

Answer : A

SLB and Auto Scaling are two Alibaba Cloud services that can work together to provide high availability, scalability, and performance for your applications. SLB is a load balancing service that distributes incoming traffic across multiple ECS instances. Auto Scaling is a service that automatically adjusts the number of ECS instances based on your business needs. When you use SLB and Auto Scaling together, you need to follow some best practices and precautions to ensure the optimal performance and reliability of your system.One of the precautions is that SLB instances must have Health Check enabled, or they cannot be used together with Auto Scaling1. Health Check is a feature of SLB that monitors the health status of the backend ECS instances. If an ECS instance becomes unhealthy or fails, SLB automatically stops sending traffic to that instance and redirects the traffic to other healthy instances. This ensures that your application can continue to serve user requests without interruption. Health Check is also essential for Auto Scaling, because Auto Scaling relies on the health status reported by SLB to decide whether to add or remove ECS instances. If an ECS instance is unhealthy, Auto Scaling will automatically replace it with a new one. If the traffic increases and the average health status of the ECS instances decreases, Auto Scaling will automatically add more instances. If the traffic decreases and the average health status of the ECS instances increases, Auto Scaling will automatically remove some instances. Therefore, Health Check is a prerequisite for using SLB and Auto Scaling together. If you disable Health Check, SLB and Auto Scaling will not be able to communicate with each other and coordinate their actions. This may result in performance degradation, service interruption, or resource waste. The other options are incorrect, because they are not necessary or relevant for using SLB and Auto Scaling together. The backend ECS instances under the same SLB instance can have different operating systems, configurations, and scaling groups, as long as they can provide the same service and respond to the same requests. SLB and Auto Scaling do not impose any restrictions on these aspects of the ECS instances.Reference:Associate SLB instances with or disassociate SLB instances from a scaling group

Answer : C

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, when ECS is used with Auto Scaling, the number of ECS instances is automatically adjusted based on traffic.Reference: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.

Answer : A

Auto Scaling is a management service that can automatically adjust elastic computing resources based on your business needs and policies.It can help you cope with traffic spikes, reduce costs, and improve service availability1.Auto Scaling supports adding an existing ECS instance into the scaling group, which is a collection of ECS instances that share the same scaling configuration and scaling rules2.However, the existing ECS instance must meet certain requirements, one of which is that the instance and the scaling group must be in the same region3. A region is a physical location where Alibaba Cloud deploys its data centers.Each region consists of multiple isolated zones that have independent power grids and networks4. Therefore, the instance and the scaling group do not have to be in the same zone, as long as they are in the same region.

Answer : D

Auto Scaling is a management service that can automatically adjust elastic computing resources based on your business needs and policies.Auto Scaling supports the following features12:

Elastic Scale-Out: Automatically adds ECS instances to handle increased workloads.

Elastic Scale-In: Automatically removes ECS instances to reduce costs when workloads decrease.

Elastic Self-Health: Automatically replaces unhealthy ECS instances to ensure high availability and reliability.

Scheduled Scaling: Automatically adds or removes ECS instances based on predefined schedules.

Predictive Scaling: Automatically predicts future workloads and adjusts ECS instances accordingly.

Elastic Self-Diagnostic is not a feature supported by Alibaba Cloud Auto Scaling.It is a fictitious term that does not exist in the Alibaba Cloud documentation or course materials.Reference:1: Auto Scaling: Automatically Adjusts Computing Resources - Alibaba Cloud2: Auto Scaling:What is Auto Scaling? - Alibaba Cloud