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Elastic Compute Service:Local disks

Last Updated:Nov 15, 2023

Local disks are located on the physical machines that host their associated Elastic Compute Service (ECS) instances. Local disks provide local storage for ECS instances. Local disks are cost-effective and offer high random IOPS, high throughput, and low latency.

Limits

  • All of the local disks for an instance reside on a single physical machine. This increases single point of failure (SPOF) risks. The durability of data stored on a local disk is determined by the reliability of the associated physical machine.

    Warning

    For example, data stored on local disks may be lost when a hardware failure occurs on their associated physical machine. We recommend that you store only temporary data on local disks.

    • To ensure data availability, we recommend that you implement data redundancy at the application layer. You can use deployment sets to distribute ECS instances across multiple physical machines for high availability and disaster recovery purposes. For more information, see Create a deployment set.

    • If your applications do not utilize an architecture that prioritizes data reliability, we recommend that you use cloud disks or a backup service with ECS instances to improve data reliability. For more information, see Disks or What is Cloud Backup?

  • After you purchase an ECS instance that has local disks attached, you must log on to the instance to partition and format the local disks. For more information, see Initialize a data disk whose size does not exceed 2 TiB on a Linux instance or Initialize a data disk up to 2 TiB in size on a Windows instance.

  • Local disks do not support the following operations:

    • Create a separate local disk.

    • Use a snapshot to create a local disk.

    • Attach a local disk.

    • Detach and release a local disk.

    • Resize a local disk.

    • Re-initialize a local disk.

    • Create a snapshot for a local disk.

    • Use a snapshot to roll back a local disk.

Local disk categories

Note

This topic provides information about local disks that are purchased together with ECS instances. For more information about the performance of instance families that are equipped with local SSDs and big data instance families, see Overview of instance families.

Local disks are suitable for scenarios that require high storage I/O performance, mass storage, and high cost efficiency. Alibaba Cloud provides two categories of local disks. The following table describes the categories.

Category

Instance family

Scenario

Local NVMe SSD

The following instance families use local NVMe SSDs:

  • Instance families equipped with local SSDs: i4, i4g, i4r, i3, i3g, i2, i2g, i2ne, i2gne, and i1

  • GPU-accelerated compute-optimized instance family: gn5

Instance families equipped with local NVMe SSDs are suitable for the following scenarios:

  • I/O-intensive applications that require high I/O performance and low latency, such as online gaming, e-commerce, live streaming, and media

  • Applications that require high storage I/O performance and a high-availability architecture at the application layer, such as NoSQL databases (including Cassandra, MongoDB, and HBase), MPP data warehouses, and distributed file systems

Local SATA HDD

The d3s, d2c, d2s, d1ne, and d1 big data instance families use local SATA HDDs.

Local SATA HDDs are the preferred storage media for industries such as Internet and finance that have high requirements for big data computing, storage, and analytics. These disks are suited for mass storage and offline computing scenarios and can meet the high requirements of distributed computing services such as Hadoop in terms of storage performance, storage capacity, and internal bandwidth.

Performance of local disks

Local NVMe SSDs

Note

You can test the bandwidth, IOPS, and latency of local NVMe SSDs to obtain the benchmark performance data and measure the Quality of Service (QoS) of Alibaba Cloud local disks. For more information, see the Commands used to test the performance of local disks section of the "Test the performance of block storage devices" topic.

  • The following table describes the performance metrics of local NVMe SSDs that the d3c compute-intensive big data instance family uses.

    Metric

    Single-disk performance

    ecs.d3c.3xlarge

    ecs.d3c.7xlarge

    ecs.d3c.14xlarge

    Maximum read IOPS

    100,000

    100,000

    200,000

    400,000

    Maximum read throughput

    4 GB/s

    4 GB/s

    8 GB/s

    16 GB/s

    Maximum write throughput

    2 GB/s

    2 GB/s

    4 GB/s

    8 GB/s

  • The following table describes the performance metrics of the local NVMe SSDs that the i4 instance family uses.

    Metric

    ecs.i4.large

    ecs.i4.xlarge

    ecs.i4.2xlarge

    ecs.i4.4xlarge

    ecs.i4.8xlarge

    ecs.i4.16xlarge

    ecs.i4.32xlarge

    Maximum read IOPS

    112,500

    225,000

    450,000

    900,000

    1,800,000

    3,600,000

    7,200,000

    Maximum read throughput

    0.75 GB/s

    1.5 GB/s

    3 GB/s

    6 GB/s

    12 GB/s

    24 GB/s

    48 GB/s

    Maximum write throughput

    0.375 GB/s

    0.75 GB/s

    1.5 GB/s

    3 GB/s

    6 GB/s

    12 GB/s

    24 GB/s

  • The following table describes the performance metrics of the local NVMe SSDs that the i4g and i4r instance families use.

    Metric

    ecs.i4g.4xlarge and ecs.i4r.4xlarge

    ecs.i4g.8xlarge and ecs.i4r.8xlarge

    ecs.i4g.16xlarge and ecs.i4r.16xlarge

    ecs.i4g.32xlarge and ecs.i4r.32xlarge

    Maximum read IOPS

    250,000

    500,000

    1,000,000

    2,000,000

    Maximum read throughput

    1.5 GB/s

    3 GB/s

    6 GB/s

    12 GB/s

    Maximum write throughput

    1 GB/s

    2 GB/s

    4 GB/s

    8 GB/s

  • The following table describes the performance metrics of the local NVMe SSDs that the i3 instance family uses.

    Metric

    ecs.i3.xlarge

    ecs.i3.2xlarge

    ecs.i3.4xlarge

    ecs.i3.8xlarge

    ecs.i3.13xlarge

    ecs.i3.26xlarge

    Maximum read IOPS

    250,000

    500,000

    1,000,000

    2,000,000

    3,000,000

    6,000,000

    Maximum read throughput

    1.5 GB/s

    3 GB/s

    6 GB/s

    12 GB/s

    18 GB/s

    36 GB/s

    Maximum write throughput

    1 GB/s

    2 GB/s

    4 GB/s

    8 GB/s

    12 GB/s

    24 GB/s

    Note

    The performance data in the preceding table represents the highest performance levels of local storage in the i3 instance family. We recommend that you use images that contain Linux kernel 4.10 or later, such as Alibaba Cloud Linux 2 and CentOS 8 images, to obtain optimal performance.

  • The following table describes the performance metrics of the local NVMe SSDs that the i3g instance family uses.

    Metric

    ecs.i3g.2xlarge

    ecs.i3g.4xlarge

    ecs.i3g.8xlarge

    ecs.i3g.13xlarge

    ecs.i3g.26xlarge

    Maximum read IOPS

    125,000

    250,000

    500,000

    750,000

    1,500,000

    Maximum read throughput

    0.75 GB/s

    1.5 GB/s

    3 GB/s

    4.5 GB/s

    9 GB/s

    Maximum write throughput

    0.5 GB/s

    1 GB/s

    2 GB/s

    3 GB/s

    6 GB/s

    Note

    The performance data in the preceding table represents the highest performance levels of local storage in the i3g instance family. We recommend that you use images that contain Linux kernel 4.10 or later, such as Alibaba Cloud Linux 2 and CentOS 8 images, to obtain optimal performance.

  • The following table describes the performance metrics of the local NVMe SSDs that the i2 and i2g instance families use.

    Metric

    Single-disk performance

    Overall instance performance

    ecs.i2.xlarge and ecs.i2g.2xlarge

    Other i2 and i2g instance types

    Maximum capacity

    894 GiB

    1,788 GiB

    8 × 1,788 GiB

    Maximum read IOPS

    150,000

    300,000

    1,500,000

    Maximum read throughput

    1 GB/s

    2 GB/s

    16 GB/s

    Maximum write throughput

    0.5 GB/s

    1 GB/s

    8 GB/s

    Access latency

    Within microseconds

    Overall instance performance data in the preceding table applies only to the ecs.i2.16xlarge instance type and represents the highest performance levels of local storage in the i2 instance family.

  • The following table describes the performance metrics of the local NVMe SSDs that the i2ne and i2gne instance families use.

    Metric

    ecs.i2ne.xlarge and ecs.i2gne.2xlarge

    ecs.i2ne.2xlarge and ecs.i2gne.4xlarge

    ecs.i2ne.4xlarge and ecs.i2gne.8xlarge

    ecs.i2ne.8xlarge and ecs.i2gne.16xlarge

    ecs.i2ne.16xlarge

    Maximum capacity

    894 GiB

    1,788 GiB

    2 × 1,788 GiB

    4 × 1,788 GiB

    8 × 1,788 GiB

    Maximum read IOPS

    250,000

    500,000

    1,000,000

    2,000,000

    4,000,000

    Maximum read throughput

    1.5 GB/s

    3 GB/s

    6 GB/s

    12 GB/s

    24 GB/s

    Maximum write throughput

    1 GB/s

    2 GB/s

    4 GB/s

    8 GB/s

    16 GB/s

    Access latency

    Within microseconds

    Note

    To obtain the maximum throughput performance of disks for Linux instances, we recommend that you use the latest versions of Alibaba Cloud Linux 2 images. Otherwise, Linux instances may be unable to deliver their maximum IOPS.

  • The following table describes the performance metrics of the local NVMe SSDs that the i1 instance family uses.

    Metric

    Single-disk performance

    Overall instance performance

    Maximum capacity

    1,456 GiB

    2,912 GiB

    Maximum IOPS

    240,000

    480,000

    Write IOPS

    min{165 × Capacity, 240,000}

    2 × min{165 × Capacity, 240,000}

    Read IOPS

    Maximum read throughput

    2 GB/s

    4 GB/s

    Read throughput

    min{1.4 × Capacity, 2,000} MB/s

    2 × min{1.4 × Capacity, 2,000} MB/s

    Maximum write throughput

    1.2 GB/s

    2.4 GB/s

    Write throughput

    min{0.85 × Capacity, 1,200} MB/s

    2 × min{0.85 × Capacity, 1,200} MB/s

    Access latency

    Within microseconds

    Items in the formulas used to calculate the performance specifications of a single local NVMe SSD:

    • In the formula used to calculate the write IOPS, each GiB of capacity produces 165 write IOPS for a maximum of 240,000 IOPS.

    • In the formula used to calculate the write throughput, each GiB of capacity produces a write throughput of 0.85 MB/s for a maximum of 1,200 MB/s.

    Overall instance performance data in the preceding table applies only to the ecs.i1.14xlarge instance type and represents the highest performance levels for local storage in the i1 instance family.

Local SATA HDDs

Note

You can test the bandwidth, IOPS, and latency of local SATA HDDs to obtain the benchmark performance data and measure the QoS of Alibaba Cloud local disks. For more information, see the Commands used to test the performance of local disks section of the "Test the performance of block storage devices" topic.

The following table describes the performance metrics of local SATA HDDs.

Metric

d1 and d1ne

d2c

d2s

Single-disk performance

Overall instance performance

Single-disk performance

Overall instance performance

Single-disk performance

Overall instance performance

Maximum capacity

5,500 GiB

154,000 GiB

3,700 GiB

44,400 GiB

7,300 GiB

219,000 GiB

Maximum throughput

190 MB/s

5,320 MB/s

190 MB/s

2,280 MB/s

190 MB/s

5,700 MB/s

Access latency

Within milliseconds

Note

Overall instance performance data in the preceding table applies only to the ecs.d1.14xlarge, ecs.d1ne.14xlarge, ecs.d2c.24xlarge, and ecs.d2s.20xlarge instance types and represents the highest performance levels for local storage in the corresponding instance families.

Billing

Local disks are billed along with the instances to which they are attached. For more information, see Subscription and Pay-as-you-go.

Disk initialization sequence

When you use an image to create an instance that has local disks attached, disks on the created instance are initialized based on the following rules:

  • Rule 1: If the image does not contain data disk snapshots, the local disks are initialized prior to the cloud disks that are created together with the instance.

  • Rule 2: If the image contains data disk snapshots, the data disks created from the snapshots are initialized in the order of data disk device names that are recorded in the image. The other disks on the instance are initialized based on Rule 1.

The following section provides an example on how disks are initialized based on Rule 2. In this example, an instance created from a Linux image that contains two data disk snapshots is used.

  • If the data disk device names recorded in the image are /dev/xvdb and /dev/xvdc, Alibaba Cloud first allocates /dev/xvdb and /dev/xvdc as device names to the data disks created from the image. The system disk is initialized first. Then, the data disks are initialized in the following sequence: data disk 1 created from the image, data disk 2 created from the image, local disk 1, local disk 2, cloud disk 1, cloud disk 2, and so on. The following figure shows the sequence in which the disks are initialized.规则二原理图1

  • If the data disk device names recorded in the image are /dev/xvdc and /dev/xvdd, Alibaba Cloud first allocates /dev/xvdc and /dev/xvdd as device names to the data disks created from the image. Then, Alibaba Cloud allocates other available device names in alphabetic order to the local disks first and then to other disks. The system disk is initialized first. Then, the data disks are initialized in the following sequence: local disk 1, data disk 1 created from the image, data disk 2 created from the image, local disk 2, cloud disk 1, cloud disk 2, and so on. The following figure shows the sequence in which the disks are initialized.规则二原理图2

Lifecycle

A local disk shares the same lifecycle as the instance to which it is attached. For more information, see Instance lifecycle.

Impacts of instance operations on data stored on local disks

The following table describes the impacts of instance operations on data stored on local disks.

Instance operation

Data stored on local disks

Local disk

Restart the operating system, restart an instance by using the ECS console, or forcefully restart an instance.

Retained

Retained

Shut down the operating system, stop an instance by using the ECS console, or forcefully stop an instance.

Retained

Retained

Automatically recover an instance.

Erased

Erased

Release an instance

Erased

Erased

When a subscription instance expires or when you have an overdue payment for a pay-as-you-go instance, the instance is stopped but has not been released.

Retained

Retained

When a subscription instance expires or when you have an overdue payment for a pay-as-you-go instance, the instance is stopped and then released.

Erased

Erased

Manually renew an expired subscription instance.

Retained

Retained

Reactivate a pay-as-you-go instance that was stopped due to an overdue payment.

Retained

Retained

References

For information about retired local SSDs, see Previous-generation disks - local SSDs.

For information about how to handle system events of instances that are equipped with local disks, see O&M scenarios and system events for instances equipped with local disks.