ACA-Cloud1 Sample Questions Answers

Alibaba Cloud relational database service (RDS) is a stable, reliable and elastic online database service that supports various database engines, such as MySQL, SQL Server, PostgreSQL, MariaDB, and PPAS (PostgreSQL with Oracle compatibility)1. RDS provides high availability, backup and recovery, security, and monitoring features for your databases. RDS does not support Oracle database, which is a proprietary database system developed by Oracle Corporation2. If you need to use Oracle database on Alibaba Cloud, you can deploy it on an ECS instance or use the Oracle Database Backup Service3.

References: 1: Alibaba Cloud Academy, “RDS Concepts”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-5-rds-concepts  2: Oracle, “Oracle Database”, https://www.oracle.com/database/  3: Alibaba Cloud, “Oracle Database Backup Service”, https://www.alibabacloud.com/product/oracle-database-backup-service

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. References: ACA Cloud Computing Certification - Alibaba Cloud Academy, Server Load Balancer - Alibaba Cloud Academy, Session Persistence - Alibaba Cloud Documentation Center

According to the Alibaba Cloud Academy, a cloud disk snapshot is a point-in-time backup of a cloud disk. You can use snapshots to back up data, create images, or restore data. The operations that you can do on a cloud disk snapshot are snapshot creation, snapshot deletion, snapshot rollback, and snapshot sharing. Snapshot duplicate and snapshot download are not the operations that you can do on a cloud disk snapshot. Therefore, the options A and C are the correct answers. References: Snapshot Overview - Alibaba Cloud Documentation Center, ACA Cloud Computing Exam Preparation Course - Alibaba Cloud, Module 3: Cloud Computing Storage, Lesson 2: Snapshot, Slide 2

 An ECS image is a copy of data from one or more disks that are attached to an ECS instance. You cannot retrieve data directly from an ECS image and use it right away. You need to create an ECS instance from the image first, and then access the data on the disks of the instance. References: Elastic Compute Service:Image overview

Session state data is the information that is associated with a specific user session, such as user preferences, shopping cart items, authentication tokens, etc. Session state data needs to be stored in a persistent and scalable way, so that it can be accessed by multiple web servers and survive server failures. Therefore, the suitable services for storing session state data are those that provide reliable, distributed, and high-performance data storage, such as RDS and Table Store.

RDS (Relational Database Service) is a fully managed online database service that supports various database engines, such as MySQL, SQL Server, PostgreSQL, MariaDB, and PPAS (PostgreSQL with Oracle compatibility)1. RDS provides high availability, backup and recovery, security, and monitoring features for your databases. RDS can store session state data in relational tables, and you can use SQL queries to access and manipulate the data.

Table Store is a fully managed NoSQL database service that provides consistent, scalable, and high-performance data storage for structured and semi-structured data2. Table Store organizes data in tables, rows, and columns, and supports primary key and attribute columns. Table Store can store session state data in flexible schemas, and you can use primary key queries or secondary index queries to access and manipulate the data.

References: 1: Alibaba Cloud Academy, “RDS Concepts”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-5-rds-concepts  2: Alibaba Cloud Academy, “Table Store”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-7-table-store

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.

References: 1: Alibaba Cloud Academy, “Auto Scaling”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-6-auto-scaling  2: Alibaba Cloud, “Scaling group”, https://www.alibabacloud.com/help/doc-detail/25948.htm  3: Alibaba Cloud, “Add an existing ECS instance to a scaling group”, https://www.alibabacloud.com/help/doc-detail/25949.htm  4: Alibaba Cloud, “Regions and zones”, https://www.alibabacloud.com/help/doc-detail/40654.htm

 RDS allows users to create multiple databases in one RDS instance, as long as the total storage capacity and performance of the instance are not exceeded. This can help users save costs and simplify management. Users can create, delete, and manage databases in the RDS console or by using SQL commands. However, databases with the same name are not allowed in the same instance, and resources are shared among the databases in the same RDS instance, such as CPU, memory, disk, and network bandwidth. References: Operate and Manage a Relational Database on the Cloud, Alibaba RDS Course | Cloud Academy, ACA Cloud Computing Certification - Alibaba Cloud Academy

 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.

References: 1: OSS Overview 2: OSS Backup

 You can create a custom image for ECS using data disk snapshots or system disk snapshots. A snapshot is a backup of the data on a disk at a specific point in time. You can use snapshots to create custom images, which are copies of the operating system and applications on a disk. You can use custom images to create ECS instances that have the same operating system, applications, and data as the original disk12.

You cannot create a custom image for ECS using CPU snapshots or memory snapshots. These are not valid terms in Alibaba Cloud. CPU and memory are not persistent storage devices, and they do not store the operating system and applications that are required for creating a custom image34. References: 1: Create a custom image from a snapshot - Alibaba Cloud1 2: What is a custom image? - Alibaba Cloud2 3: What is a CPU? - Alibaba Cloud3 4: What is memory? - Alibaba Cloud4

Alibaba Cloud Server Load Balancer (SLB) is a service that distributes network traffic across multiple ECS instances to improve the service capabilities of applications. SLB supports different load balancing algorithms, such as round robin, weighted round robin, and least connections. When using the weighted round robin algorithm, SLB assigns different weights to backend ECS instances based on their processing capabilities. The higher the weight of a backend ECS instance, the more requests it will receive from SLB. However, the weight of a backend ECS instance is not the only factor that determines the load distribution. The number and the weight of other backend ECS instances in the same server group also affect the load balancing result. Therefore, without knowing the weight settings of the remaining 4 ECS instances, we cannot tell what would happen to the load distribution among the 5 ECS instances. The other statements are incorrect because they assume a fixed or proportional load distribution based on the weight of ecs_inst1, which is not necessarily true.

References:

• Alibaba Cloud Server Load Balancer
• [ACA Cloud Computing Certification Exam Preparation Course]
• Alibaba Cloud Computing Exam Question 2022

SQL injection is a common application layer attack that targets the database of a web application. SQL injection exploits a security vulnerability in the application’s software, such as incorrect filtering of user input, that allows an attacker to send malicious SQL statements to the database. These statements can then be executed to steal, modify, or delete data, or even execute commands on the server1. SQL injection can also bypass authentication and authorization mechanisms, and sometimes even impersonate or damage the underlying system2. SQL injection is one of the most common and dangerous web attacks, and it can cause serious damage to the confidentiality, integrity, and availability of web applications3. References: 1: SQL Injection - OWASP2: SQL Injection - Web Application Firewall - Alibaba Cloud Documentation Center3: Web Application Firewall:What is WAF? - Alibaba Cloud.

Alibaba Cloud Architecture Design Training is a service that provides professional guidance and best practices for designing cloud architectures that meet the business requirements and goals of the company. Alibaba Cloud Architecture Design Training can help the company to understand the cloud migration process, select the appropriate Alibaba Cloud products and services, design a secure, reliable, scalable, and cost-effective cloud architecture, and implement the migration plan with minimal risks and disruptions. Alibaba Cloud Architecture Design Training can also help the company to optimize the performance and efficiency of the cloud system after the migration.

References:

• Alibaba Cloud Architecture Design Training
• Cloud Migration - Alibaba Cloud Solutions
• ACA-Cloud1 Alibaba Exam Questions and Answers - CertLibrary

Domain name binding is a feature that allows you to use your own domain name to access your OSS bucket, instead of using the default OSS domain name. Domain name binding has the following requirements and limitations12:

• Your customized domain name will be audited by Alibaba Cloud. You need to submit a domain name binding request and wait for approval before you can use your own domain name to access your OSS bucket.
• Your customized domain name need to be put on record in MIIT (Ministry of Industry and Information Technology). This is a mandatory requirement for all websites that are hosted in mainland China. You need to provide your domain name information and relevant documents to MIIT and obtain an ICP filing number before you can use your own domain name to access your OSS bucket.

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.

Using a cloud computing service is simple and straightforward. One can choose the instance with desired specification, finish payment and then use it right away. Moreover, the underlying physical machines are managed by cloud service providers and transparent to users. This is the basic concept of cloud computing, which provides on-demand, scalable, and reliable computing resources and services over the internet12. References: 1: ACA Cloud Computing Exam Preparation Course - Alibaba Cloud3 2: What Is Alibaba Cloud Academy Certification?4

 Cloud disks are reliable because they use a distributed file management system with 3 redundant copies to provide block-level data storage for ECS instances, ensuring 99.9999999% data reliability. This means that the data stored on cloud disks is automatically replicated across three different physical servers in the same zone. If one server fails, the data can still be accessed from the other two servers. Cloud disks also support snapshot backup and recovery, which can help users restore data to a previous point in time in case of accidental deletion or corruption. References: Elastic Compute Service (ECS) - Alibaba Cloud Academy, Cloud Disk - Alibaba Cloud Documentation Center

An ECS disk can be used jointly or separately to meet the requirements of different application scenarios. ECS disks are categorized into ephemeral SSD disks and cloud disks. Compared with ephemeral SSD disks, cloud disks are more reliable as they use a triplicate distributed system to provide block-level data storage for ECS instances, ensuring 99.9999999% data reliability.

Alibaba Cloud does not support intranet communication between products that are not in the same region, which means that ECS instances in different regions cannot communicate with each other on the intranet, and ECS instances and other products in different regions, such as ApsaraDB for RDS and OSS instances, cannot communicate with each other on the intranet. However, this does not mean that Server Load Balancer cannot be deployed for ECS instances in various regions. Server Load Balancer is a service that distributes traffic among multiple ECS instances according to the configured forwarding rules. It can be used to balance the load and improve the service availability and fault tolerance of applications. Server Load Balancer supports cross-region deployment, which means that it can distribute traffic to ECS instances in different regions12. References: 1: ACA Cloud Computing Exam Preparation Course - Alibaba Cloud3 2: Server Load Balancer - Alibaba Cloud Documentation Center4

Alibaba Cloud OSS service provides different methods for file uploading, such as simple upload, multipart upload, append upload, and resumable upload1. However, not all of these methods support resuming from break point, which is a feature that allows you to resume an interrupted upload from where it left off. The only method that supports resuming from break point is resumable upload, which is based on multipart upload and uses a checkpoint file to record the upload progress2. The other methods do not support resuming from break point, and will either overwrite or append to the existing object if the upload is interrupted and retried.

References: 1: Alibaba Cloud Academy, “OSS Upload Methods”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-2-oss-upload-methods  2: Alibaba Cloud, “Resumable upload”, https://www.alibabacloud.com/help/doc-detail/31991.htm