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Elastic Compute Service:Block storage performance

Last Updated:Jan 18, 2024

Various block storage devices, such as cloud disks and local disks, have different performance metrics and specifications. Familiarize yourself with performance metrics and select block storage devices that are suitable for specific workloads and applications based on your storage capacity requirements and the performance metrics. This topic describes the performance metrics and specifications of cloud disks and local disks.

Performance metrics

The key metrics that are used to measure the performance of block storage devices include IOPS, throughput, and latency. Specific block storage devices have capacity requirements. For example, enhanced SSDs (ESSDs) at different performance levels (PLs) have different capacity ranges.

  • IOPS

    IOPS measures the number of read/write operations that can be performed per second. High IOPS is critical for transaction-intensive applications such as database applications. A standard SSD can deliver the maximum IOPS only when the standard SSD is attached to an I/O optimized instance. For information about instances of which instance families are I/O optimized instances, see Overview of instance families. The following table describes the common IOPS metrics.

    Metric

    Description

    Data access method

    Total IOPS

    The total number of I/O operations per second.

    Access locations on storage devices in a continuous or non-continuous manner.

    Random read IOPS

    The average number of random read I/O operations per second.

    Access locations on storage devices in a non-continuous manner.

    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.

    Access locations on storage devices in a continuous manner.

    Sequential write IOPS

    The average number of sequential write I/O operations per second.

  • Throughput

    Throughput measures the amount of data that is transferred per second. Unit: MB/s. High throughput is critical for applications such as Hadoop offline computing applications that require a large number of sequential read/write operations.

  • Latency

    Latency measures the amount of time that is required for a block storage device to process an I/O request. Unit: seconds, milliseconds, or microseconds. High latency may cause performance to degrade or lead to errors in applications that require low latency.

    • For latency-sensitive applications such as database applications, we recommend that you use ESSD AutoPL disks, ESSDs, standard SSDs, or local SSDs.

    • For latency-insensitive applications that require high throughput such as Hadoop offline computing applications, we recommend that you use Elastic Compute Service (ECS) instances of the d1 or d1ne instance family to which local SATA HDDs are attached.

  • Capacity

    Capacity is the amount of storage space. Unit: TiB, GiB, MiB, or KiB. Block storage capacity is measured in binary units. For example, 1 GiB is equal to 1,024 MiB.

    You cannot use capacity as a metric to measure the performance of block storage devices, but the performance of block storage devices varies based on the capacity of the devices. A block storage device that has a larger capacity provides stronger processing capabilities. Block storage devices of the same category have the same I/O performance per unit capacity. However, the performance of a cloud disk linearly increases together with the disk capacity up to the single-disk maximum performance of the disk category. ESSDs in different capacity ranges have different PLs.

For information about how to test the performance of different categories of block storage devices, see Test the performance of block storage devices and Test the IOPS performance of an ESSD.

Performance of cloud disks

The following table describes the performance and common usage scenarios of different categories of cloud disks.

Item

ESSD AutoPL disk

ESSD

ESSD Entry disk

Standard SSD

Ultra disk

Basic disk

PL

An ESSD AutoPL disk can decouple capacity from performance and deliver a baseline performance that is equal to the baseline performance of an ESSD PL1 disk. You can configure provisioned performance and burst performance for ESSD AutoPL disks.

PL3

PL2

PL1

PL0

None.

None.

None.

None.

Single-disk capacity range (GiB)

1 to 65,536

1,261 to 65,536

461 to 65,536

20 to 65,536

1 to 65,536

10 to 32,768

20 to 32,768

20 to 32,768

5 to 2,000

Max IOPS/Min IOPS

1,000,000/3,000

1,000,000/64,850

100,000/24,872

50,000/2,800

10,000/1,812

6,000/1,880

25,000/2,400

5,000/1,960

Several hundreds

Max throughput/Min throughput (MB/s)

4,096/125

4,000/750.5

750/350.5

350/130

180/100

150/101.5

300/130

140/103

30~40

Formula for calculating the IOPS per disk

Baseline performance:

max{min{1,800 + 50 × Capacity, 50,000}, 3,000}

Provisioned performance: min{Provisioned IOPS, 50,000}

Burst performance: min{IOPS supported by the instance type, 1,000,000}

min{1,800 + 50 × Capacity, 1,000,000}

min{1,800 + 50 × Capacity, 100,000}

min{1800 + 50 × Capacity, 50,000}

min{1,800+12 × Capacity, 10,000}

min{1,800 + 8 × Capacity, 6,000}

min{1,800 + 30 × Capacity, 25,000}

min{1,800 + 8 × Capacity, 5,000}

None.

Formula for calculating the throughput per disk (MB/s)

Baseline performance:

max{min{120 + 0.5 × Capacity, 350}, 125}

Provisioned performance: min{16 KB × Provisioned IOPS/1,024, Maximum throughput per disk}

Burst performance: min{Throughout supported by the instance type, 4 GB/s}

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{100 + 0.15 × Capacity, 150}

min{120 + 0.5 × Capacity, 300}

min{100 + 0.15 × Capacity, 140}

None.

Data durability

99.9999999%

99.9999999%

99.9999999%

99.9999999%

99.9999999%

99.9999999%

99.9999999%

99.9999999%

99.9999999%

Average one-way random write latency in milliseconds (block size = 4 KB)

0.2

0.2

0.2

0.2

0.3~0.5

1~3

0.5~2

1~3

5~10

  • The performance of standard SSDs varies based on the size of data blocks. Smaller data blocks have lower throughput and higher IOPS. The following table provides a comparison of the data blocks.

    Data block size (KiB)

    Maximum IOPS

    Throughput

    4

    Approximately 25,000

    Approximately 100

    16

    Approximately 17,200

    Approximately 260

    32

    Approximately 9,600

    Approximately 300

    64

    Approximately 4,800

    Approximately 300

  • In the following examples, a standard SSD is used to describe how to calculate single-disk performance:

    • Single-disk maximum IOPS: The baseline IOPS is 1,800. The IOPS increases by 30 per additional GiB to up to 25,000.

    • Single-disk maximum throughput: The baseline throughput is 120 MB/s. The throughput increases by 0.5 MB/s per additional GiB to up to 300 MB/s.

  • Basic disks are cloud disks of a previous generation and are no longer available for purchase.

Performance of local disks

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

  • For information about how to test the performance of local disks on i4p instances.