ApsaraDB RDS for PostgreSQL offers the Enterprise SSD (ESSD) and general ESSD storage types. This topic describes the storage types and the differences between the storage types. This topic also provides purchase suggestions on storage types.
Description
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.
The ESSD and general ESSD storage types meet the reliability, durability, and read/write performance goals that are specified in the Alibaba Cloud service level agreement (SLA). ESSDs use a distributed storage architecture that supports 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.
ESSD
ESSDs offered by Alibaba Cloud deliver ultra-high performance and use the next-generation distributed block storage architecture. ESSDs are integrated with 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. ESSDs can reduce one-way latencies and process up to 1 million read and write requests at random per second. ESSDs are provided in the following performance levels (PLs):
PL1 ESSD: This is the basic PL of ESSDs.
PL2 ESSD: A PL2 ESSD delivers IOPS and throughput that are approximately twice the IOPS and throughput delivered by a PL1 ESSD.
PL3 ESSD: A PL3 ESSD delivers IOPS that is up to 20 times the IOPS delivered by a PL1 ESSD and delivers throughput that is up to 11 times the throughput delivered by a PL1 ESSD. PL3 ESSDs are suitable for scenarios in which highly concurrent requests must be processed with high I/O performance and at low read and write latencies.
General ESSD
General ESSDs are compatible with all features of ESSDs and deliver better baseline I/O performance than PL1 ESSDs. In addition, general ESSDs provide the I/O burst, I/O acceleration, and data archiving features. For more information about the supported features, see Use the I/O burst feature, Use the I/O acceleration feature, and Use the data archiving feature. For more information about general ESSDs, see What is a general ESSD?
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.
Performance items of the storage type
Item | ESSD | General ESSD |
I/O performance | ★★★★★
| ★★★★★★ Delivers better baseline performance than PL1 ESSDs and supports the I/O burst and I/O acceleration features in addition to all features of ESSDs. The following list describes the I/O performance of general ESSDs:
|
Configuration flexibility | ★★★★★ Provides various configuration options and allows you to change the storage capacity of an RDS instance. Note You can reduce the storage capacity of RDS instances that meet specific requirements. For more information, see Change instance specifications. | ★★★★★ Provides various configuration options and allows you to change the storage capacity of an RDS instance. Note You can reduce the storage capacity of RDS instances that meet specific requirements. For more information, see Change instance specifications. |
Backup method | Provides snapshot backups. | Provides snapshot backups. |
Time required for backup, read-only instance creation, and instance cloning | ★★★★★ Requires a few seconds. | ★★★★★ Requires a few seconds. |
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. |
Impact of storage capacity expansion | Imposes no impacts. | Imposes no impacts. |
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. |
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 are fluctuating, and you want to enable the I/O burst feature.
Your RDS instance contains a large number of infrequently accessed or modified tables, and you want to enable the data archiving feature.
If cloud disks of specific PLs are required, you can purchase ESSDs.
References
For more information about general ESSDs, see General ESSDs.
For more information about the I/O burst feature of general ESSDs, see Use the I/O burst feature.
For more information about the I/O acceleration feature of general ESSDs, see Use the I/O acceleration feature.
For more information about the data archiving feature of general ESSDs, see Use the data archiving feature of general ESSDs.
For more information about how to change the storage type from ESSD to general ESSD, see Manage general ESSDs.
For more information about the frequently asked questions about storage capacity, see FAQ about storage capacity.