Elastic ephemeral disks-Elastic Compute Service(ECS)-阿里云帮助中心

Overview

Compare elastic ephemeral disks with local disks

Elastic ephemeral disks offer flexible capacity, unlike local disks that can only be purchased with ECS instances.

For performance comparison, please refer to Block storage performance.

Item	Elastic ephemeral disk	Local disk
Cost-effectiveness	Priced independently.	Not priced independently. Cost is included in the instance price and can fluctuate.
Flexibility	Customizable capacity with resize support, eliminating redundant resource costs. Can be created with an instance or separately. Supports detach and release.	Capacity is fixed by ECS instance type and cannot be resized. Important To increase capacity, you must purchase additional compute and storage resources, which can be wasteful. Can only be created and released with specific ECS instance types. Does not support detach or release.
Maintainability	Recoverable within hours after a failure.	After a failure, the disk cannot be repaired quickly. You must wait for maintenance or replace the instance.

Use cases

Temporary data storage

Stores intermediate computation results, cache data, and temporary files.
High performance computing

Provides high-performance temporary storage for tasks requiring high IOPS (hundreds of thousands to millions) and high throughput (hundreds of MB/s to several GB/s).

Lifecycle

An elastic ephemeral disk's lifecycle is partially tied to its associated ECS instance.

For subscription ECS instances, elastic ephemeral disks use subscription billing. The disk is released when the instance expires. With an overdue payment, existing disks remain usable but new purchases are blocked. See Subscription.
For pay-as-you-go ECS instances, elastic ephemeral disks become unavailable with an overdue payment. See Pay-as-you-go.

See Overdue payments.

Billing

Billable items and billing rules

You are charged for disk capacity. Both pay-as-you-go and subscription billing methods are supported. See Elastic ephemeral disk billing.
Pricing

For pricing, see Block Storage Pricing.

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

Supported 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 but cannot be reattached to another instance.	Yes
Release	Yes Important Releasing the instance also releases the attached elastic ephemeral disk.	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

Elastic ephemeral disks come in two categories: standard (large capacity, high throughput) and premium (small capacity, high IOPS).

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. Note the following for elastic ephemeral disks:
- In the Region and Network and Zone section, select a supported region and zone.
- In the Instance section, select a supported instance type.
- Expand the Block 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 other parameters, see Create an instance with Custom Launch.
  
  Note
  The maximum number of elastic ephemeral disks depends on the instance type. You can attach up to 16 disks.

Create separately

Go to ECS console - Block Storage - Disks.
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 other parameters, see Create a data disk.
Attach the disk to an ECS instance and initialize it.

See Attach a data disk.

References

Elastic ephemeral disks have functional limitations compared to other cloud disks. See Features.

Supported operations:

FAQs

How reliable are elastic ephemeral disks?

The target failure rate is higher than other cloud disks but lower than local disks. Although Alibaba Cloud uses multiple technologies to reduce failures, data loss can still occur.

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

Elastic ephemeral disks lack the high reliability, online resizing, and data protection features of ESSD-series cloud disks. An elastic ephemeral disk cannot be reattached to another instance.