This topic describes the performance metrics and specifications of various block storage devices, including cloud disks and local disks.
Performance metrics
The key metrics used to measure the performance of block storage devices include IOPS, throughput, and latency. Some block storage devices also 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 committed IOPS only when it is attached to an I/O optimized instance. For information about whether an instance is an I/O optimized instance, 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 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 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 applications such as Hadoop offline computing applications that require high throughput but not low latency, we recommend that you use Elastic Compute Service (ECS) instances of the d1 or d1ne instance family that have local SATA HDDs 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 equals 1,024 MiB.
Capacity cannot be used as a metric to measure the performance of block storage devices. However, the performance of block storage devices varies based on their capacity. 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 with its capacity up to the single-disk maximum performance of the disk category. ESSDs in different capacity ranges have different PLs.
For more 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 typical use scenarios of different categories of cloud disks.
Item | ESSD AutoPL | ESSD | Standard SSD | Ultra disk | Basic disk ③ | |||
PL | An ESSD AutoPL disk can decouple capacity from performance and deliver a baseline performance equal to that of an ESSD PL1 disk. You can also configure provisioned performance and burst performance for the ESSD AutoPL disk. | PL3 | PL2 | PL1 | PL0 | N/A | N/A | N/A |
Single-disk capacity range (GiB) | 40~65,536 | 1,261~65,536 | 461~65,536 | 20~65,536 | 20~65,536 | 20~32,768 | 20~32,768 | 5~2,000 |
Maximum IOPS | 1,000,000 | 1,000,000 | 100,000 | 50,000 | 10,000 | 25,000 ① | 5,000 | Several hundreds |
Maximum throughput (MB/s) | 4,096 | 4,000 | 750 | 350 | 180 | 300 ① | 140 | 30~40 |
Formula used 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{1800 + 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} | N/A |
Formula used to calculate single-disk throughput (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} | N/A |
Data durability | 99.9999999% | 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 K) | 0.2 | 0.2 | 0.2 | 0.2 | 0.3~0.5 | 0.5~2 | 1~3 | 5~10 |
① The performance of standard SSDs varies based on the sizes of data blocks. Smaller data blocks have 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 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 until it reaches the maximum IOPS 25,000.
Single-disk maximum throughput: The baseline throughput is 120 MB/s. The throughput increases by 0.5 MB/s per additional GiB until it reaches the maximum throughput 300 MB/s.
③ 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 Non-Volatile Memory Express (NVMe) SSDs and SATA HDDs, see Local disks.