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Elastic Compute Service:Disks

Last Updated:Feb 08, 2024

Alibaba Cloud disks are block-level data storage resources for Elastic Compute Service (ECS). Alibaba Cloud disks provide low latency, high performance, high durability, and high reliability. Alibaba Cloud disks use a distributed triplicate mechanism to ensure 99.9999999% (nine 9's) data durability for ECS instances. If service disruptions due to hardware failures occur within a zone, data within the zone is copied to an available disk in another zone to ensure data durability and availability. This topic describes the disk categories, disk performance specifications, and how to use disks.

Disk categories

Disks are classified into the following categories based on their performance:

  • ESSD AutoPL disks: You can configure the burst performance and provisioned performance of ESSD AutoPL disks based on your business requirements. ESSD AutoPL disks inherit the features and performance of enhanced SSDs (ESSDs) and provide the capability of decoupling disk capacity from disk performance. For more information, see ESSD AutoPL disks.

    We recommend that you use ESSD AutoPL disks in the following scenarios:

    • Scenarios for which ESSDs are suitable, such as large-sized online transactional processing (OLTP) databases, NoSQL databases, and Elasticsearch, Logstash, and Kibana (ELK) distributed logs.

    • Scenarios in which disk performance needs to be increased without extending disk capacity.

    • Scenarios in which business workloads significantly fluctuate and disks need to burst their performance when workload spikes occur.

  • ESSDs: ESSDs are based on the next-generation distributed block storage architecture and utilize 25 Gigabit Ethernet and remote direct memory access (RDMA). Each ESSD has low one-way latency and can deliver up to 1,000,000 random read/write IOPS. For more information, see ESSDs.

    We recommend that you use ESSDs for scenarios such as OLTP databases, NoSQL databases, and ELK distributed logs.

  • Standard SSDs: Standard SSDs are high-performance disks that provide consistent high random IOPS and high data reliability.

    We recommend that you use standard SSDs for scenarios such as I/O-intensive applications, small and medium-sized relational databases, and NoSQL databases.

  • ESSD Entry disks: ESSD Entry disks provide enterprise-grade features and data protection capabilities. We recommend that you use ESSD Entry disks as system disks or for scenarios such as development and testing.

    Note

    You can attach ESSD Entry disks only to instances of the u1 and e instance families. For information about the instance families, see the u1, universal instance family section in the "Universal instance families" topic and the e, economy instance family section in the "Shared instance families" topic.

  • Ultra disks: Ultra disks are cost-effective and provide medium random IOPS and high data reliability. We recommend that you use ultra disks as system disks for scenarios such as development and testing.

  • Basic disks: Basic disks are the previous generation of disks and are unavailable for purchase.

The following table describes the performance of disks of different categories.

Item

ESSD AutoPL disk

ESSD

ESSD Entry disk

Standard SSD

Ultra disk

Basic disk

PL3

PL2

PL1

PL0

Single-disk capacity range (GiB)

1~65,536

1,261~65,536

461~65,536

20~65,536

1~65,536

10~32,768

20~32,768

20~32,768

5~2,000

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{1,800 + 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{Throughput 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.

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

API parameter value

cloud_auto

cloud_essd

cloud_essd

cloud_essd

cloud_essd

cloud_essd_entry

cloud_ssd

cloud_efficiency

cloud

For more information about disk performance, see Block storage performance.

Disks are classified into system disks and data disks based on their purposes.

  • System disks contain operating systems and can be created only along with instances. The lifecycle of a system disk is the same as the lifecycle of the instance to which the system disk is attached.

  • Data disks are used to store application data and can be created separately or along with instances.

Note

When a disk is created, the disk capacity displayed in the ECS console includes the capacity occupied by the operating system, and the remaining available capacity may be less than the disk capacity displayed in the ECS console. For example, if the capacity of a system disk displayed in the ECS console is 40 GiB, the remaining available capacity may be less than 40 GiB because the operating system occupies some disk capacity.

Limits

A disk can be attached only to a single ECS instance within the same zone.

Note

When you create an ESSD, you can enable the multi-attach feature for the ESSD. This way, the disk can be attached to multiple ECS instances at the same time. For more information, see Enable multi-attach.

The limits described in the following table also apply.

Item

Requirement or limit

Adjust the quota

Permissions to create pay-as-you-go disks

To create disks within the Chinese mainland, you must first complete real-name verification.

N/A

Maximum number of pay-as-you-go disks

You can view the resource quota in the ECS console. For more information, see View and increase resource quotas.

N/A

Maximum number of system disks on a single instance

1

N/A

Maximum number of data disks on a single instance

64

Note

You can attach up to 16 data disks to an instance when you create the instance. If the instance requires more data disks, attach more data disks after the instance is created. The maximum number of disks that can be attached to an instance varies with instance types. For more information, see Overview of instance families.

N/A

Capacity of all pay-as-you-go ultra disks within an account

You can view the resource quota in the ECS console. For more information, see View and increase resource quotas.

N/A

Capacity of all pay-as-you-go standard SSDs within an account

You can view the resource quota in the ECS console. For more information, see View and increase resource quotas.

N/A

Capacity of all pay-as-you-go enhanced SSDs (ESSDs) within an account

You can view the resource quota in the ECS console. For more information, see View and increase resource quotas.

N/A

Capacity of a single basic disk

5 GiB to 2,000 GiB

N/A

Capacity of a single standard SSD

20 GiB to 32,768 GiB

N/A

Capacity of a single ultra disk

20 GiB to 32,768 GiB

N/A

Capacity of a single ESSD

  • PL0 ESSDs: 1 GiB to 65,536 GiB

  • PL1 ESSDs: 20 GiB to 65,536 GiB

  • PL2 ESSDs: 461 GiB to 65,536 GiB

  • PL3 ESSDs: 1,261 GiB to 65,536 GiB

N/A

Capacity of a single ESSD AutoPL disk

1 GiB to 65,536 GiB

N/A

Capacity of a single ESSD Entry disk

10 GiB to 32,768 GiB

N/A

Capacity of a single local SSD

5 GiB to 800 GiB

N/A

Capacity of all local SSDs on an instance

1,024 GiB

N/A

Capacity of a single system disk

  • Windows Server: 40 GiB to 2,048 GiB

  • FreeBSD: 30 GiB to 2,048 GiB

  • Linux distributions excluding CoreOS: 20 GiB to 2,048 GiB

Note

Basic disks are the previous generation of disks that are unavailable for purchase. If you use basic disks as system disks, the capacity upper limit for each basic disk is 500 GiB.

N/A

Permissions to attach new local disks to instances that are equipped with local disks

New local disks cannot be attached to instances that are already equipped with local disks.

N/A

Permissions to change configurations of instances that are equipped with local disks

Only bandwidth configurations of instances that are equipped with local disks can be changed.

N/A

Mount points of system disks

/dev/vda

N/A

Mount points of data disks

/dev/vd[b-z]

N/A

Billing

For information about the billing of disks, visit the Pricing tab on the Elastic Compute Service product page.

Disks support the subscription and pay-as-you-go billing methods. For more information, see Subscription and Pay-as-you-go.

  • The subscription billing method is supported for disks that are created along with subscription instances or separately created for subscription instances.

  • The pay-as-you-go billing method is supported for disks that are created along with pay-as-you-go instances or separately created. Storage capacity units (SCUs) can be used to offset the bills of pay-as-you-go disks.

After a disk is created, you can change its billing method. For more information, see Switch the billing method of disks.

Related operations

The following table describes the operations that you can perform on disks.

Operation

References

Attach an idle pay-as-you-go disk to an ECS instance

  1. Attach a data disk

  2. Format the data disk based on the operating system. For more information, see the following topics:

Create and prepare a data disk

  1. Create a disk

  2. Attach a data disk

  3. Format the data disk based on the operating system. For more information, see the following topics:

Encrypt data stored on a disk

For more information, see Overview.

For more information about how to encrypt disks, see the following topics:

Resize a system disk or data disk

For more information, see Overview.

Replace the operating system of an instance

Replace the operating system of an instance

Back up data stored on a disk

Restore a disk to its initial state

Re-initialize a system disk

Restore a disk to its state at a specific point in time

Roll back a disk by using a snapshot

Detach a damaged system disk from an instance and attach the disk back to the instance after the disk is repaired

Detach or attach a system disk

Release an instance but retain data stored on its system disk

Detach or attach a system disk

Release a subscription disk that is no longer needed to reduce costs

  1. Change the billing method of a cloud disk

  2. Detach a data disk

  3. Release a disk

Release a pay-as-you-go disk that is no longer needed to reduce costs

  1. Detach a data disk

  2. Release a disk