PolarDB-X allows you to restore historical data from backups. This topic describes how to restore
data.
Method
PolarDB-X allows you to restore data by point in time. This method depends on data backup and
log backup. You can restore data to a specific point in time within the backup time
range. The time can be accurate to seconds. For example, if a data backup set of an
instance was created at 00:00:01 on January 1, 2021 and log backup is enabled, you
can restore data to any second since 00:00:01 on January 1, 2021.
Global consistency
PolarDB-X is a distributed database service. In PolarDB-X, data is stored on multiple data
nodes. If distributed transactions exist in an instance, the instance to which data
is restored must ensure that data is consistent among data nodes.
In the preceding figure, a table that records account balances is stored in PolarDB-X. The data in the table is distributed to two data nodes. The sum of the account balances
is CNY 200. In this example, distributed transactions are used to transfer money between
different accounts.
At 16:14:20 on July 25, 2021, Account C transferred CNY 30 to Account A, and Account
D transferred CNY 20 to Account C. If you want to restore data to 16:14:20 on July
25, 2021 and ensure global consistency, you can restore data only to the specific
point in time before or after the transactions are processed. In this case, the sum
of account balances must equal CNY 200, as shown in Restoration 2 in the preceding
figure. In this scenario, data cannot be restored based on Restoration 1 that is shown
in the preceding figure. If data is restored based on Restoration 1, the sum of account
balances during data restoration equals CNY 250. This causes global inconsistency.
Restore data to a new instance
PolarDB-X can restore data only to a new instance. After data is restored, we recommend that
you use data transmission tools such as Data Transmission Service (DTS) to migrate
data back to the original instance.
- The new instance to which the data is restored and the original instance must contain
the same IP addresses and CIDR blocks in their whitelists, and use the same backup
and parameter configurations.
- The data in the new instance is the same as the data in the backup file or the data
at the specified point in time.
- The information about the account that is used to create the data backup or log backup
is replicated to the new instance.
- The new instance and the original instance use the same topology. This means that
the number of nodes in the new instance is the same as the number of nodes in the
original instance.
Pricing and billing method
Data is restored to a new instance. You are charged for using the new instance.
Precautions
If you want to restore data to a specific point in time, make sure that the log backup
feature is enabled. When you configure a data backup policy, the retention period
for log backups must be more than 0.
Restore data to a specific point in time
- Log on to the PolarDB-X console.
- In the top navigation bar, select the region where the target instance is located.
- On the Instances page, click the PolarDB-X 2.0 tab.
- Find the target instance and click its ID.
- Click Recovery.
- On the page that appears, configure the following parameters.
Parameter |
Description |
Instance to Be Restored |
The ID of the instance that you want to restore. |
Restoration Type |
This parameter is set to Clone. You do not need to specify this parameter.
|
Restoration Time |
The point in time to which you want to restore data.
Note The earliest point in time to which you can restore data is the time when the first
backup set is created.
|
Region and Zone |
By default, the values of the two parameters are the same as those of the original
instance. You do not need to specify the two parameters.
|
Network Type |
The network type can only be VPC. You cannot change the network type.
|
VPC |
Make sure that the PolarDB-X cluster is created in the same VPC as the ECS instance to which you want to connect.
Otherwise, the cluster and the ECS instance cannot communicate over the internal network
to achieve optimal performance.
Note Before you configure a VPC, make sure that a VPC and a vSwitch are available in the
selected region and the selected zone. For more information, see Create and manage a VPC.
|
vSwitch |
The vSwitch of the instance to which the data is restored. |
Compatibility |
By default, this parameter is set to the MySQL version of the original instance. You
do not need to specify this parameter.
|
Node Specifications |
You are charged for PolarDB-X based on the node specifications and the number of nodes. You can configure this
parameter to specify the number of CPU cores and memory size for the instance. For
more information, see Instance types.
|
Nodes |
By default, the number of nodes in the instance to which the data is restored is the
same as the number of nodes in the original instance. You cannot change this value.
|
Storage Type |
By default, the storage type of the instance to which the data is restored is the
same as the storage type of the original instance. You do not need to specify this
parameter.
|
Storage Cost |
By default, each node provides 3 TB of storage. You do not need to specify the storage
capacity for each node when you create a PolarDB-X instance. If you select the pay-as-you-go
billing method for your PolarDB-X instance, you can be charged for storage fees per
hour.
|
Duration |
Select the subscription duration of the instance.
Note This parameter is available only when the Product Type parameter of the original instance
is set to Subscription.
|
Quantity |
By default, this parameter is set to 1. You cannot change this value. |
- Select PolarDB-X 2.0 (Subscription) Terms of Service and click Buy Now.
- On the Purchase page, confirm the unpaid order and the payment method, and click Purchase.
- After you complete the payment, the specified number of instances requires approximately
10 to 15 minutes to be created. After the instances are created, you can return to
the Instance List page of the PolarDB-X console to view the newly created instances.