Elastic ephemeral disks - Elastic Compute Service - Alibaba Cloud Documentation Center

An elastic ephemeral disk is a block storage device that can be created alongside an Elastic Compute Service (ECS) instance or separately created, with user-defined capacity for temporary data storage. It features high performance and cost-effectiveness. This topic describes the specifications, billing, limits, and common operations of elastic ephemeral disks.

Overview

Compare elastic ephemeral disks with local disks

Elastic ephemeral disks are block storage devices that offer flexible capacity, unlike local disks, which can only be purchased alongside ECS instances.

Item	Elastic ephemeral disk	Local disk
Cost-effectiveness	Priced independently.	Local disks are not priced independently. Their cost is included in the instance price and can fluctuate.
Maximum performance	IOPS: 1 million Throughput: 4 GB/s	IOPS: 900,000 Throughput: 6 GB/s
Flexibility	You can customize the capacity and resize the disk. This eliminates the need to pay for redundant resources. Can be created with an instance or separately. Supports independent operations such as detach and release.	Capacity is fixed based on the ECS instance type and cannot be resized. Important To increase capacity, purchase additional compute and storage resources, which can be wasteful. Can only be created and released with specific ECS instance types. Does not support independent operations such as detach and release.
Maintainability	You can recover the disk within hours after a failure.	After a failure, the disk cannot be repaired quickly. You must wait for maintenance or replace the instance, making maintenance difficult and time-consuming.

Use cases

Temporary data storage
Ideal for storing temporary data, such as intermediate computation results, cache data, and temporary files.
High performance computing
Elastic ephemeral disks provide high-performance temporary storage for computing tasks that require high IOPS (from hundreds of thousands to millions) and high throughput (from hundreds of MB/s to several GB/s).

Lifecycle

The lifecycle of an elastic ephemeral disk is partially tied to its associated ECS instance.

If you have a Subscription ECS instance, you can only use the Subscription billing method for its elastic ephemeral disks. The disk's lifecycle is tied to the instance and the disk is automatically released when the instance expires. If you have an overdue payment, you can continue to use your existing elastic ephemeral disks but cannot purchase new ones. For more information, see Subscription.
If you have a Pay-as-you-go ECS instance, you cannot use its elastic ephemeral disks if you have an overdue payment. For more information, see Pay-as-you-go.

For more information about overdue payments, see Overdue payments.

Billing

Billable items and billing rules
You are charged for the capacity of your elastic ephemeral disks. This disk supports both pay-as-you-go and subscription billing methods. For more information, see Billing of elastic ephemeral disks.
Pricing
For information about the pricing of elastic ephemeral disks, see ECS Product Page.

Limitations

Supported regions

Standard elastic ephemeral disks: Zones B, J, and K in China (Hangzhou), Zones M, N, and E in China (Shanghai), Zones F, I, and L in China (Beijing), Zone B in China (Chengdu), Zones A, B, and C in Singapore, and Zones A, B, and C in Germany (Frankfurt).
Premium elastic ephemeral disks: Zone J in China (Hangzhou), Zones M and N in China (Shanghai), Zone I in China (Beijing), Zone B in China (Chengdu), Zone A in Japan (Tokyo), and Zone D in China (Hong Kong).

Supported instance families

Elastic ephemeral disks support the following instance families:

Features

Feature	Support for elastic ephemeral disks	Support for other disks
Create independently	Yes	Yes
Attach/Detach independently	Yes Important An elastic ephemeral disk can be detached independently, but it cannot be reattached to another instance.	Yes
Release	Yes Important Releasing the instance also releases the disk when an elastic ephemeral disk is attached.	Yes
Initialize	Yes	Yes
Resize	Yes	Yes
Create snapshots/Roll back from snapshots	No	Yes
Encryption	No	Yes
Multi-attach	No	Yes
Asynchronous replication	No	Yes
Switch billing method independently	Yes	Yes
Change disk category	No	Yes
Use as a system disk	No	Yes

Categories and performance

Two categories of elastic ephemeral disks are available: standard and premium. Standard elastic ephemeral disks are suitable for scenarios with large data volumes and high throughput needs, while premium elastic ephemeral disks are suitable for scenarios requiring small capacity but high IOPS. The following table describes the performance of each type:

Metric	Standard elastic ephemeral disks	Premium elastic ephemeral disks
Single-disk capacity range (GiB)	64 to 8,192	64 to 8,192
Maximum read IOPS per disk	Either 100 times the capacity or 820,000, whichever is smaller	Either 300 times the capacity or 1,000,000, whichever is smaller
Maximum write IOPS per disk	Either 20 times the capacity or 160,000, whichever is smaller	Either 150 times the capacity or 500,000, whichever is smaller
Maximum read throughput per disk (MB/s)	Either 0.8 times the capacity or 4,096, whichever is smaller	Either 1.6 times the capacity or 4,096, whichever is smaller
Maximum write throughput per disk (MB/s)	Either 0.4 times the capacity or 2,048, whichever is smaller	Either the capacity or 2,048, whichever is smaller
Write I/O density①	20	150
Read I/O density①	100	300

①: I/O density = IOPS / disk capacity, unit: IOPS/GiB, indicating the IOPS capability per GiB.

Use elastic ephemeral disks

Create an elastic ephemeral disk

Create with an instance

Go to the ECS instance buy page.
Click the Custom Launch tab
Configure the mandatory parameters such as Billing Method, Region, Instance Type, and Image. Take note of the following parameters when creating an elastic ephemeral disk:
- In the Region and Network and Zone section, select the appropriate region and zone for the elastic ephemeral disk.
- In the Instance section, select a supported instance type.
- Expand the Storage section, select Elastic Ephemeral Disk | NAS File System | Dedicated Block Storage Cluster (Optional), and click Add Elastic Ephemeral Disk.
- Specify the category, size, and quantity of the elastic ephemeral disk.
  For information about other parameters, see Custom launch.
  Note
  The number of elastic ephemeral disks that you can attach depends on the instance type. You can attach a maximum of 16 elastic ephemeral disks.

Create separately

Go to ECS console - Block Storage.
On the Elastic Ephemeral Disk tab, click Create Elastic Ephemeral Disk.
Set the configuration parameters.
- Select a region and zone that support elastic ephemeral disks.
- Select the type and capacity of the elastic ephemeral disk.
For more information about other parameters, see Create an empty data disk.
To use the disk, attach it to an ECS instance and initialize it.
For more information, see Attach a data disk.

Related operations

Compared to other cloud disks, elastic ephemeral disks have some functional limitations. For more information, see Features.

For details on supported operations, see the following topics:

FAQs

How reliable are elastic ephemeral disks?

Its target failure rate is higher than other cloud disks but lower than local disks. While Alibaba Cloud employs multiple technologies to reduce the failure rate, data loss can still occur.

How do elastic ephemeral disks differ from ESSD-series cloud disks?

Elastic ephemeral disks do not offer the same high reliability, online resizing capabilities, or multiple data protection and disaster recovery features available with ESSD-series cloud disks. Additionally, an elastic ephemeral disk cannot be reattached to another instance.