Alibaba Cloud Certified Associate (ACA) Exam Study Notes

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Table Of Contents

Preparation

Virtualized using XEN/KVM
Uses Apsara distributed file system Pangu for storage
For example, ecs.sn1.3xlarge sn is the instance family, 1 is the generation and 3xlarge is the instance size
ECS Bare Metal Instances are a compute service that combines the elasticity of virtual machines and the performance and features of physical machines
If you stop an instance, then you won’t be billed. However, you will be charged for the underlying disk storage.
If you want to reset the password for an instance, then you need to restart the ECS instance.
Once you assign an EIP (Elastic IP Address) to your instance, you can’t assign an internet IP back to the instance. You can only detach the EIP and use the private IP of the instance.
For a disk rollback, ECS must be in a stopped state.
If you had created a custom image from a snapshot, then you need to delete the image first before being allowed to delete the snapshot.
You need to stop an instance if you want to perform these operations - instance upgrade, disk replace, IP change.
When you replace a system disk, a new disk ID is assigned and the old one is removed. You can then change the disk size, image and key pair.
Instance metadata can be retrieved at http://100.100.100.200/latest/meta-data
User metadata can be retrieved at http://100.100.100.200/latest/user-data

Disk Type	Properties
System	Maximum number of disks per instance: 1 A system disk must be created with an instance and shares the same lifecycle as the instance Shared access to a system disk is not allowed The minimum size of a system disk depends on the image
Data	Maximum number of disks per instance: 16 It can be created separately or together with an ECS instance. Data disk size is up to 32 TB

Disk Category	Properties
Ultra disk	Ultra disks feature high cost-effectiveness, medium random IOPS performance, and high data reliability
Standard SSD	Standard SSDs are high-performance disks that feature consistent and high random IOPS performance and high data reliability
Enhanced SSD (ESSD)	ESSDs are based on the next-generation distributed block storage architecture and the 25 Gigabit Ethernet (25GE) and remote direct memory access (RDMA) technologies. Each ESSD can deliver up to one million random IOPS and has low latency.

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RDS comes in three flavors - Basic, HA, Finance (Enterprise)
HA → 1 master 1 slave configuration
Finance → 1 master 2 slave configuration
1 instance can have up to 2 TB storage
RDS instance can be created in single/multiple zones
Data recovery options - Master node rollback/Slave node repair/Temporary instance with backup
Temporary instance with backup is valid for 48 hours
You can create Read-Only instance to reduce read pressure
Security options - IP whitelisting, DDos, SQL Injection prevention
DTS used for Structural migration (tables, views etc.), full migration or incremental migration

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OSS is a PAAS service
Up to 50 PB data can be stored in a single bucket
Data is replicated with three copies in AZs
With a PUT request, you can upload up to 5 GB of data
With a Multi-part request, you can upload up to 48.8 TB of data
You cannot delete a non-empty bucket
Use x-oss-process parameter for img processing
Image processing supports parameter mode (image/<action>) and style mode: (style/<style_name>)
Anti-leech (Hotlink) supports wildcard * & ? or empty referer

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Supports scheduled and dynamic scaling
During a cool down, only scaling requests from cloud monitor alarm are rejected, manual scaling is still allowed
No rollback of scaling activities incase of an ecs failure
SLB & RDS defined in the scaling group cannot be modified
Deleting a scaling group does not delete RDS/SLB
Scheduled task is retried if any scaling activity was running on previous attempt
Alarm tasks name must be unique

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