KRDS instance types
KRDS supports the following instance types: high availability instance, three-node enterprise edition instance, temporary instance, read-only instance, and standalone instance.
High availability instance
- A basic high availability instance contains two instance objects: a master instance and a standby instance. The standby instance is invisible to users. High availability instances support automatic failover. When the master instance encounters a fault, the system automatically switches the service to the standby instance. The failover is completed within 5 seconds and does not affect the service of the high availability instance. High availability instances are the most widely purchased type of instances.
Three-node enterprise edition instance
- A basic three-node enterprise edition instance contains three instance objects: a master instance and two replica instances. The replica instances are invisible to users. The Raft protocol is used to maintain strong consistency among the three nodes. Three-node enterprise edition instances support automatic failover, which is completed within 5 seconds. Three-node enterprise edition instances are ideal for scenarios that demand high data consistency.
- A basic temporary instance contains only one instance object that is visible to users. A basic temporary instance does not have a hot standby instance object. Temporary instances are ideal for testing performance or validating data after data restoration. You can create a temporary instance from data at any time point in the last seven days. After you validate the data, you can upgrade the temporary instance to a high availability instance. This way, you can complete data backtracking.
- A read-only instance contains only one instance object that is visible to users. If a database receives a large amount of reads and infrequent writes, a single instance may not withstand the pressure of read demands, and the business may be affected. To elastically scale the read capacity and even out the pressure, you can create one or more read-only instances in a region to increase throughput and satisfy the read demands. Read-only instances can improve the overall performance in specific scenarios.
- A standalone instance contains only one instance object. A standalone instance does not suffer the additional performance overhead caused by data replication to a standby instance. Therefore, a standalone instance has better performance than a high availability instance of the same configuration. With the separation of computing and storage, faults that occur on a computing node do not cause data loss. Standalone instances can greatly reduce cost because less database nodes are required.
The connection number of KRDS refers to the maximum number of concurrent connections that are allowed from applications to a KRDS instance.
You can create read-only instances for your high availability instances. Data on a high availability instance is replicated to its read-only instances.
Limits on primary and read-only instances
- A primary instance must be a high availability instance.
- The storage capacity of a read-only instance must be greater than or equal to its primary instance. We recommend that you configure the same memory size for a primary instance and its read-only instance.
- A read-only instance inherits the access control policies from its primary instance.
- The parameter settings of a read-only instance are independent from its primary instance. You can determine whether to synchronize parameter changes made to a primary instance to its read-only instances.
- When you restart a primary instance, its read-only instances do not restart synchronously.
- The configuration changes made to a primary instance do not affect data replication to its read-only instances.
KRDS character set
A connection to a KRDS instance involves three types of character sets: client character set, database character set, and default server character set. The three character sets must use the same encoding. If one of the three uses a different encoding from the others, garbled characters appear in text. You can change the character set encoding on your database client. Alternatively, you can contact Kingsoft Cloud to change the database encoding to that used by your client. However, if you want to use a new encoding, you must request Kingsoft Cloud to change the database encoding accordingly. When you use KRDS, we recommend that you use an easy-to-use client that provides comprehensive features and supports MySQL. The client allows you to easily change the character set encoding and enhances your work efficiency. The open source MySQL Workbench and Navicat are all good choices.
Availability zones refer to physical data centers located in the same region, with their electrical and network infrastructure isolated from each other. A region contains one or more availability zones. A fault that occurs in one availability zone does not affect other availability zones. This can protect your applications and databases from being affected by a single point of failure (SPOF).
In addition, compared with a single data center, availability zones provide higher availability, fault tolerance, and scalability. Note the following information when you use availability zones:
- The cloud resources in different availability zones of the same region can access each other through private IP addresses.
- Not all regions have the same number of availability zones.
- An availability zone is an identifier that is defined for users to select resource locations. Services of different users in the same availability zone may reside in different physical data centers.
A virtual private cloud (VPC) is a logically isolated section on Kingsoft Cloud where you can launch Kingsoft Cloud resources in a virtual network that you define. You have complete control over your VPC. For example, you can select your own IP address range, create subnets, and configure route tables and gateways. You can use IPv4 in your VPC for secure and easy access to resources and applications.
An endpoint subnet allows you to establish private connections between a VPC and other Kingsoft Cloud services, such as KRDS and Kingsoft Cloud Standard Storage Service (KS3). This way, the Kingsoft Cloud services can access the VPC without using the Internet or the Network Address Translation (NAT) service.