You can split or merge shards to adjust the number of active shards, which determine the maximum read and write capacities of Simple Log Service Logstores. A shard can be automatically split. However, you must manually merge shards. This topic describes how to split, merge, and delete shards. This topic also describes how to configure automatic sharding.
Term
Data in Simple Log Service is stored in shards. Simple Log Service uses shards to manage the read and write capacities of Logstores, Eventstores, and Metricstores. When you create a Logstore, a Metricstore, or an Eventstore, you must specify the number of shards. After the Logstore, Metricstore, or Eventstore is created, you can split or merge shards to increase or decrease the number of shards. For more information, see Shard.
Split a shard
We recommend that you plan the number of shards based on your actual data traffic. Each shard supports a write speed of up to 5 MB/s or 500 write operations per second, and a read speed of up to 10 MB/s or 100 read operations per second. The limits are not hard limits. If a limit is exceeded, Simple Log Service continues to read or write data. However, performance may be degraded. If the read and write traffic of data exceeds the read or write capacity of a shard, you can split the shard into multiple shards to increase the capacity.
If the error code 403 or 500 is frequently returned when you write data by calling Simple Log Service API, you can go to the CloudMonitor console to check the traffic and status codes. Then, you can determine whether to increase the number of shards.
Log on to the Simple Log Service console.
In the Projects section, click the project you want.
On the tab, move the pointer over the logstore you want and choose
> Modify. 
On the Logstore Attributes page, click Modify.
Find the shard that you want to split and click Split in the Actions column.
ImportantYou can split only a shard that is in the readwrite state.
Select the number of new shards into which you want to split the original shard, and click OK.
Click Save.
View shards
Log on to the Simple Log Service console.
In the Projects section, click the project you want.
On the tab, move the pointer over the logstore you want and choose
> Modify. On the Logstore Attributes page, view the shards in the logstore.
Automatic sharding
Simple Log Service provides the automatic sharding feature to automatically handle business traffic that exceeds the estimated value. Shards are automatically split only if the following conditions are met:
Automatic Sharding is turned on.
The data write speed exceeds the maximum write speed of the current shard for more than 5 minutes.
The number of shards that are in the readwrite state does not exceed the specified maximum number of shards in your Logstore.
Automatic sharding is not performed on the shards that are split from a shard within the previous 15 minutes.
You can enable the automatic sharding feature when you create or modify a Logstore. If you turn on Automatic Sharding, you must configure the Maximum Shards parameter.
Automatic Sharding
For example, a Logstore contains four shards. Simple Log Service checks whether each shard meets the splitting conditions. The shards that meet the splitting conditions are split. The total number of new shards does not exceed the specified maximum number of shards.
Maximum Shards
This parameter specifies the maximum number of new shards that can be obtained after shards are automatically split. After you enable the automatic sharding feature, up to 256 shards that are in the readwrite state can be obtained after splitting.
Merge shards
If the read and write traffic of data is very small compared with the maximum read and write capacities of your shard, we recommend that you merge shards to reduce the fees of active shards. You can find your shard and click Merge in the Actions column to merge shards. Simple Log Service automatically finds a shard that is adjacent to your shard and merges the two shards. Two shards are considered adjacent if the MD5 hash ranges for the shards form a contiguous range with no gaps. Shards can only be manually merged.
When you merge shards, you must specify a shard that is in the readwrite state. You cannot specify the last shard that is in the readwrite state.
On the tab, move the pointer over the logstore you want and choose
> Modify. On the Logstore Attributes page, click Modify.
Find the shard that you want to merge and click Merge in the Actions column.
Click Save.
After you merge shards, the specified shard and its adjacent shard are in the readonly state. A new shard that is in the readwrite state is generated. The MD5 hash range of the new shard covers the MD5 hash ranges of the original shards.
Delete a shard
After a shard is deleted, the shard cannot be restored. Proceed with caution.
Automatic deletion
If you specify a data retention period when you create a Logstore, the shards in the Logstore and the data that is stored in the shards are automatically deleted when the retention period ends.
Manual deletion
If you select Permanent Storage for Data Retention Period when you create a Logstore, we recommend that you delete the shards and data of the Logstore by deleting the Logstore. For more information, see Delete a Logstore.
Shard-related API operations
Action | API operation |
Split a shard | |
Query shards |