An elastic ephemeral disk is a block storage device that can be created alongside an 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
Comparison between elastic ephemeral disks and 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 | An elastic ephemeral disk is priced separately. | The price of a local disk is included in the instance price, subject to fluctuation based on the instance type. |
Maximum Performance |
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Flexibility |
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Maintainability | Elastic ephemeral disks offer high maintainability, with the ability to recover within hours after a failure. | Maintainability is limited for a local disk. Recovery from a local disk failure is not immediate. It requires waiting for maintenance or instance replacement, resulting in high maintenance complexity and extended downtime. |
Scenarios
Temporary data storage
Like local disks, elastic ephemeral disks are ideal for storing temporary data, such as temporary calculation intermediate results, cached data, and temporary files.
High performance computing
For computing tasks with high IOPS (hundreds of thousands to millions) and throughput (hundreds of MB/s to several GB/s), elastic ephemeral disks provide high-performance temporary storage support.
Lifecycle
The lifecycle of elastic ephemeral disks is partially coupled with ECS instances.
If the ECS instance is on a subscription basis, elastic ephemeral disks only support subscription. In subscription mode, they have the same lifecycle as the instance and are forcibly released upon instance expiration. If there are overdue bills in the account, you can use existing elastic ephemeral disks, but cannot perform new purchases or other fee-related operations. For more information, see Subscription.
If the ECS instance is a pay-as-you-go instance, you cannot use elastic ephemeral disks when there are overdue bills in the account. For more information, see Pay-as-you-go.
For more information about overdue payments, see Overdue payments.
Billing
Billable items and billing rules
When you use elastic ephemeral disks you are charged by disk capacity, supporting 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.
Limits
Supported regions
Elastic ephemeral disks are only available in the following regions and zones: Zone J of China (Hangzhou), Zone N of China (Shanghai), Zone I of China (Beijing), and Zone B of China (Chengdu).
Supported instance families
Elastic ephemeral disks support the following instance families:
Features
Feature | Support for elastic ephemeral disks | Support for other disks |
Create/Modify disks | Yes | Yes |
Attach/Detach disks | Yes Important Elastic ephemeral disks can be detached, but after detachment cannot be attached to other instances. | Yes |
Release disks | Yes | Yes |
Initialize disks | Yes | Yes |
Resize disks | Yes | Yes |
Create snapshots/Roll back a disk by using a snapshot | No | Yes |
Encrypt disks | No | Yes |
Multi-attach disks | No | Yes |
Asynchronously replicate disks | No | Yes |
Change disk billing method | Yes | Yes |
Change disk category | No | Yes |
Use disks as system disks | No | Yes |
Categories and performance
Based on different IOPS and throughput requirements, 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 elasitc 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 = total I/O / disk capacity, unit: IOPS/GiB, indicating the IOPS capability per GiB.
Use elastic ephemeral disks
Create an elastic ephemeral disk
Create an elastic ephemeral disk when you create an instance
Go to the ECS instance buy page.
On the Custom Launch tab, configure the mandatory parameters such as Billing Method, Region, Instance Type, and Image. Take note of the following parameters when you create an elastic ephemeral disk:
Select the appropriate region and zone for the elastic ephemeral disk in the Region and Network and Zone section.
Choose the required instance type in the Instance parameter.
Expand the Storage section, select Elastic Ephemeral Disk | NAS File System (optional), and click Add Elastic Ephemeral Disk.
Specify the category, size, and quantity of the elastic ephemeral disk.
NoteAn instance can attach up to 16 elastic ephemeral disks.
For information about other parameters, see Create an instance on the Custom Launch tab.
Separately create an elastic ephemeral disk
Log on to the ECS console.
In the left-side navigation pane, choose .
In the Elastic Ephemeral Disk tab, click Create Elastic Ephemeral Disk.
Configure the disk parameters.
Choose the supported region and zone for the elastic ephemeral disk.
Select the category and size of the elastic ephemeral disk in the Elastic Ephemeral Disk parameter.
For more information about the parameters, see Create an empty data disk.
Attach the elastic ephemeral disk to the ECS instance and perform initialization to use it.
For more information, see Attach a data disk.
Related operations
Compared to cloud disks, elastic ephemeral disks have certain usage limits and support only the following operations. For more information about limits, refer to Features.
For information about cloud disks, refer to the following topics:
FAQs
How to understand the reliability of elastic ephemeral disks?
Elastic ephemeral disk failure rate is designed to be between that of a local disk and a cloud disk. Alibaba Cloud employs various technical measures to reduce the failure rate but does not guarantee against data loss after a failure.
What are the differences between elastic ephemeral disks and ESSD-series disks?
ESSD disks offer high reliability and the ability to support online configuration changes, various data protection options, and disaster recovery features. In contrast, elastic ephemeral disks lack these capabilities and cannot be attached to other instances after detachment.