ACP-Cloud1 Exam Dumps - ACP Cloud Computing Certification

To confirm a previously unhealthy instance is now healthy, Alibaba Cloud SLB requires three consecutive successful health checks. With a health check interval of 2 seconds and a response timeout of 5 seconds, each check cycle takes up to 5 seconds. Therefore, three successive health checks would take a minimum of 5×3=155 \times 3 = 155×3=15 seconds in total. However, because the health checks are conducted at 2-second intervals, there’s overlap, reducing the actual time to at least 11 seconds for the SLB to mark the instance as healthy.

 According to the Alibaba Cloud SLB documentation1, SLB provides a health check feature that monitors the availability and performance of the backend servers. If a backend server fails the health check, SLB stops routing requests to it and redirects the traffic to other healthy servers. This way, SLB can improve the system’s availability by eliminating single points of failure (SPOFs). Therefore, option A is a correct statement about SLB.

According to the same documentation1, SLB instances are assigned with public IP addresses or private IP addresses based on the network type. If you delete an SLB instance and create a new one, a new IP address will be allocated to the new instance. You cannot specify or reserve an IP address for an SLB instance. Therefore, option B is also a correct statement about SLB.

Option C is incorrect, because SLB does not require you to install or configure any SLB agent on the backend servers. You only need to add the backend servers to the SLB instance and configure the listener and the server group. SLB will automatically distribute the traffic to the backend servers based on the load balancing algorithm and the health check status2.

Option D is also incorrect, because SLB does not provide a function to automatically synchronize data among backend servers. SLB only handles the network traffic distribution and does not interfere with the data on the backend servers. You need to use other methods or tools to synchronize data among backend servers, such as rsync, lsyncd, or Alibaba Cloud Data Transmission Service (DTS)3.

References: Server Load Balancer:SLB overview, Add backend servers, and Data Transmission Service.

Modifying the MAC address of an ECS instance’s NIC can cause network disconnection issues because Alibaba Cloud's VPC network infrastructure relies on consistent NIC configuration. Changing the MAC address may prevent the instance from being identified correctly on the network.

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Alibaba Cloud SLB can distribute user requests to backend ECS instances, but these ECS instances do not have to have the same specification (CPU, Memory). SLB virtualizes the added group of ECS instances in the same region into an application pool, and you can manage backend servers through either the default server group, a primary server group, or VServer groups. You can add ECS instances of different specifications to the same server group or VServer group according to your needs. SLB supports weighted round-robin (WRR) and weighted least connections (WLC) algorithms to balance the load among backend servers with different weights. References:

SLB overview - Alibaba Cloud

Backend server overview - Alibaba Cloud

What is Server Load Balancer and How It Works - Alibaba Cloud

Server Load Balancer - Alibaba Cloud

Alibaba Server Load Balancer (SLB) Course - Cloud Academy

SLB (Server Load Balancer) is a service that distributes network traffic across groups of backend servers to improve the service capability and application availability1. SLB supports HTTPS listeners, which allow you to encrypt the data transmission between clients and SLB instances2. HTTPS is a secure version of HTTP that uses SSL/TLS protocols to provide data encryption, integrity, and authentication3.

To use HTTPS listeners, you need to upload SSL certificates to SLB. SSL certificates are digital certificates that use public key cryptography to verify the identity of a website and encrypt the data exchanged between the website and the visitors4. There are two types of SSL certificates: server certificates and client certificates. Server certificates are issued by trusted certificate authorities (CAs) to verify the identity of the website owner and the domain name. Client certificates are issued by the website owner to verify the identity of the visitors5.

SLB supports both one-way and two-way authentication for HTTPS listeners. One-way authentication means that only the server identity is verified by the client. Two-way authentication means that both the server and the client identities are verified by each other. To use one-way authentication, you only need to upload the server SSL certificate to SLB. To use two-way authentication, you need to upload both the server SSL certificate and the client CA certificate to SLB. The client CA certificate is the root certificate or intermediate certificate of the CA that issues the client certificates.

Therefore, if you want to use SLB and ECS instances to deploy two-way authenticated HTTPS websites, you need to host server SSL certificates and client CA certificates on SLB. SLB can host both SSL certificates and CA certificates, and it supports HTTPS two-way authentication. The other statements are incorrect. References: Server Load Balancer(SLB) - Alibaba Cloud, Add an HTTPS listener - Server Load Balancer - Alibaba Cloud Documentation Center, What is HTTPS? - SSL.com, What is an SSL Certificate? - SSL.com, What is a Client Certificate? - SSL.com, [Configure two-way authentication for an HTTPS listener - Server Load Balancer - Alibaba Cloud Documentation Center]

 Changing an instance’s operating system requires creating a custom image or using a public image, and then replacing the system disk of the instance. This process will cause the instance to restart. Therefore, this statement is false. References: ECS User Guide: Replace the system disk (non-public image) and ECS User Guide: Replace the system disk (public image)

Alibaba Cloud Object Storage Service (OSS) is ideal for storing unstructured data, including media files such as pictures, videos, and documents. OSS offers scalable storage, high durability, and easy access, making it well-suited for handling large volumes of unstructured data.

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Alibaba Cloud OSS (Object Storage Service) is designed for storing large volumes of unstructured data, such as files, images, and videos, making it an optimal solution for network disk applications. By migrating storage from ECS data disks to OSS, the team can offload storage tasks, reduce the number of ECS instances required, and significantly lower O&M costs. OSS also provides high scalability, reliability, and cost-effectiveness for such use cases.