This topic describes the performance metrics and specifications of various Elastic Block Storage (EBS) devices, such as cloud disks and local disks.

Performance metrics

The key metrics used to measure EBS performance include Input/output operations per second (IOPS), throughput, and latency. Some EBS devices also have capacity requirements. For example, enhanced SSDs (ESSDs) of different performance levels (PLs) have different capacity ranges.

  • IOPS

    The IOPS metric measures the number of read/write operations that can be performed per second. The metric indicates the performance of transaction intensive applications, such as databases. A standard SSD can implement the committed IOPS performance only when it is attached to an I/O optimized instance. Common IOPS performance metrics that are measured include sequential and random operations. The following table describes these performance metrics.

    Metric Description Data access method
    Total IOPS The total number of I/O operations per second. Randomly and sequentially access locations in storage devices.
    Random read IOPS The average number of random read I/O operations per second. Randomly access locations in storage devices.
    Random write IOPS The average number of random write I/O operations per second.
    Sequential read IOPS The average number of sequential read I/O operations per second. Sequentially access locations in storage devices.
    Sequential write IOPS The average number of sequential write I/O operations per second.
  • Throughput

    The throughput metric measures the size of data transferred per second. Unit: MB/s. This metric indicates the performance of applications that require a large number of sequential read/write operations, such as Hadoop offline computing applications.

  • Latency
    Latency is the period of time required for an EBS device to process an I/O request. Unit: s, ms, or μs. High latency may cause performance degradation or errors in applications that have requirements for low latency.
    • For latency-sensitive applications such as databases, we recommend that you use ESSDs, standard SSDs, or local SSDs.
    • For applications that require high throughput but do not require low latency such as Hadoop offline computing applications, we recommend that you use ECS instances attached with local SATA HDDs of the d1 or d1ne instance family.
  • Capacity

    Capacity is the size of storage space. Unit: TiB, GiB, MiB, or KiB. EBS capacity is measured in binary units. For example, 1 GiB equals 1,024 MiB.

    You cannot use the capacity as a metric to measure the performance of EBS devices, but the performance of EBS devices varies based on capacity. The larger the capacity of an EBS device is, the stronger its processing capabilities are. EBS devices of the same type have the same I/O performance per unit capacity. However, the performance of each disk increases based on capacity until it reaches the upper limit performance for that single disk. ESSDs of different capacity ranges have different PLs.

For information about how to test the performance of different types of EBS devices, see Performance tests on Block Storage or Test the IOPS performance of an enhanced SSD.

Disk performance

The following table lists the performance and typical scenarios of different categories of disks.
Performance category ESSD Standard SSD Ultra disk Basic disk 3
PL PL3 PL2 PL1 PL0 None None None
Maximum capacity of a single disk (GiB) 1,261 to 32,768 461 to 32,768 20 to 32,768 40 to 32,768 32,768 32,768 2,000
Maximum IOPS 1,000,000 100,000 50,000 10,000 25,000 1 5,000 Several hundreds
Maximum throughput (MB/s) 4,000 750 350 180 300 1 140 30 to 40
Formula to calculate the IOPS of a single disk 2 min{1,800 + 50 × Capacity, 1,000,000} min{1,800 + 50 × Capacity, 100,000} min{1,800 + 50 × Capacity, 50,000} min{1,800 + 12 × Capacity, 10,000} min{1,800 + 30 × Capacity, 25,000} min{1,800 + 8 × Capacity, 5,000} None
Formula to calculate the throughput of a single disk (MB/s) 2 min{120 + 0.5 × Capacity, 4,000} min{120 + 0.5 × Capacity, 750} min{120 + 0.5 × Capacity, 350} min{100 + 0.25 × Capacity, 180} min{120 + 0.5 × Capacity, 300} min{100 + 0.15 × Capacity, 140} None
Data reliability 99.9999999% 99.9999999% 99.9999999% 99.9999999% 99.9999999% 99.9999999% 99.9999999%
Average single-channel random write latency in milliseconds (block size = 4 KB) 0.2 0.3 to 0.5 0.5 to 2 1 to 3 5 to 10
API parameter value cloud_essd cloud_ssd cloud_efficiency cloud
  • OLTP databases: relational databases such as MySQL, PostgreSQL, Oracle, and SQL Server databases
  • NoSQL databases: non-relational databases such as MongoDB, HBase, and Cassandra databases
  • Elasticsearch distributed logs: Elasticsearch, Logstash, and Kibana (ELK) log analysis
  • I/O intensive applications
  • Small and medium-sized relational databases
  • NoSQL databases
  • Development and test business
  • System disks
  • Applications that are not frequently accessed or have low I/O loads
  • Applications that require low costs and random I/O operations

1 The performance of standard SSDs varies based on the sizes of data blocks. Smaller data blocks result in lower throughput and higher IOPS, as described in the following table.

Data block size (KiB) Maximum IOPS Throughput (MB/s)
4 Approximately 25,000 Approximately 100
16 Approximately 17,200 Approximately 260
32 Approximately 9,600 Approximately 300
64 Approximately 4,800 Approximately 300

2 A standard SSD is used in the following examples to describe how to calculate the performance of a single disk:

  • Maximum IOPS: The baseline IOPS is 1,800 and performance increases by 30 IOPS per additional GiB of storage. The maximum IOPS is 25,000.
  • Maximum throughput: The baseline throughput is 120 MB/s and performance increases by 0.5 MB/s per additional GiB of storage. The maximum throughput is 300 MB/s.

3 Basic disks are part of a previous generation of disks and are no longer available for purchase.

Local disks

For information about the performance of local NVMe SSDs and SATA HDDs, see Local disks.