ApsaraDB RDS for MySQL offers the Enterprise SSD (ESSD), local SSD, standard SSD, and general ESSD storage types. This topic describes the differences among the storage types and purchase suggestions.
Introduction
Storage type | Description |
ESSD | ESSDs are developed by Alibaba Cloud based on the next-generation distributed block storage architecture. ESSDs deliver ultra high storage performance. ESSDs are integrated with 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. ESSDs can provide lower one-way latencies than standard SSDs and process up to 1 million read and write requests at random per second. ESSDs are provided in the following performance levels (PLs):
For more information about the ESSD performance, see ESSDs. |
Local SSD | Local SSDs reside on the same physical host as the database engine that is run by your RDS instance. You can store data in local SSDs to reduce I/O latencies. |
Standard SSD | Standard SSDs are elastic block storage devices that are designed based on a distributed storage architecture. You can store data in standard SSDs to separate computing from storage. Note Standard SSDs are being phased out. We recommend that you use ESSDs. For more information, see [EOS/Discontinuation] End of sale for the standard SSD storage type for specific database engines in ApsaraDB RDS from July 01, 2022. |
General ESSD | General ESSDs are compatible with all features of ESSDs, deliver better baseline performance than PL1 ESSDs, and provide the I/O burst, I/O acceleration, and data archiving features.
For more information, see [Product changes/Feature changes] The baseline I/O performance of the general ESSDs of ApsaraDB RDS instances is increased, Use the I/O burst feature of general ESSDs, Use the I/O acceleration feature of general ESSDs, Use the data archiving feature of general ESSDs, and What is a general ESSD? |
For more information about the differences in performance among storage types, see Block storage performance. The performance comparison items include the maximum capacity per disk, maximum IOPS, and maximum throughput.
All of the preceding storage types meet the reliability, durability, and read and write performance goals that are specified in the Alibaba Cloud service level agreement (SLA).
Local SSDs are used by RDS instances that run RDS High-availability Edition. In RDS High-availability Edition, a primary RDS instance and a secondary RDS instance are provisioned to implement high availability. If the primary RDS instance fails, a primary/secondary switchover is performed within seconds. For more information, see RDS High-availability Edition.
Standard SSDs, general ESSDs, and ESSDs use a distributed storage architecture. This architecture uses multiple data replicas to ensure data reliability. If you use RDS High-availability Edition or RDS Cluster Edition and the primary RDS instance fails, a primary/secondary switchover is performed within seconds.
View the storage type of an RDS instance
Log on to the ApsaraDB RDS console and go to the Basic Information page of the RDS instance. In the Basic Information section of the page, view the storage type of the RDS instance.
Comparison among storage types
Only RDS instances that run MySQL on RDS High-availability Edition support local SSDs.
Item | ESSD | General ESSD | Local SSD |
I/O performance | ★★★★★ Delivers higher I/O performance than standard SSDs.
| ★★★★★★ Delivers better baseline I/O performance than PL1 ESSDs and provides the I/O burst, I/O acceleration, and data archiving features. The following list describes the I/O performance of general ESSDs:
| ★★★★★ Delivers low I/O latency and high I/O performance.
|
Configuration flexibility | ★★★★★ Provides various configuration options and allows you to expand or reduce the storage capacity of an RDS instance. Note You can reduce only the storage capacity of an RDS instance that meets specific requirements. For more information, see Configuration items and Change instance specifications. | ★★★★★ Provides various configuration options and allows you to expand or reduce the storage capacity of an RDS instance. Note You can reduce only the storage capacity of an RDS instance that meets specific requirements. For more information, see Configuration items and Change instance specifications. | ★★★★ Provides various configuration options and allows you to separately adjust the storage capacity. The storage capacity of some RDS instances that use local SSDs varies based on the instance types of the RDS instances. You cannot separately adjust the storage capacity of these RDS instances. |
Backup method | Provides snapshot backups. | Provides snapshot backups. | Provides physical backups by using XtraBackup. |
Time required for backup, read-only instance creation, and instance cloning | ★★★★★ Requires a few seconds. | ★★★★★ Requires a few seconds. | ★★ Requires a few hours based on the storage capacity. |
Time required for storage capacity expansion | ★★★★★ Supports online storage capacity expansion. You can expand the storage capacity of an RDS instance within a few seconds. | ★★★★★ Supports online storage capacity expansion. You can expand the storage capacity of an RDS instance within a few seconds. | ★★★ Requires a few hours to expand the storage capacity of your RDS instance because the data needs to be replicated. |
Impact of storage capacity expansion | Imposes no impacts. | Imposes no impacts. | Triggers transient connections during storage capacity expansion. |
Data durability | ★★★★★ Delivers 99.9999999% data reliability, supports RDS instances that run RDS Basic Edition, and reduces costs. | ★★★★★ Delivers 99.9999999% data reliability, supports RDS instances that run RDS Basic Edition, and reduces costs. | ★★★★ Has a risk of data corruption due to hardware faults, which requires secondary databases to support disaster recovery. |
Purchase suggestions
We recommend that you purchase general ESSDs in the following scenarios:
The I/O loads on your RDS instance are heavy, and you want to enable the I/O acceleration feature.
The I/O loads on your RDS instance significantly fluctuate, and you want to enable the I/O burst feature.
Your RDS instance contains a large number of tables that are infrequently accessed or modified, and you want to enable the data archiving feature.
If ESSDs are required, we recommend that you purchase ESSDs of high PLs.
Product support
For more information about the storage types and features supported by different instance types, see Features.