Block Storage is a high-performance, low-latency block storage service for Alibaba Cloud Elastic Compute Service (ECS). Like a physical disk, a Block Storage device can be formatted and used to create a file system, meeting the data storage requirements of ECS-based workloads.
Applies to: ECS instances
Disk types
Block Storage offers two disk categories to match different workload requirements:
| Disk type | Best for | Key characteristics |
|---|---|---|
| Cloud disk | Transactional workloads requiring consistent I/O (databases, application servers) | Triplicate distributed architecture; low latency, high durability, high reliability; create, resize, and release at any time |
| Local disk | Throughput-intensive workloads requiring high I/O performance and cost efficiency at scale | Physical disk on the host machine; low latency, high random IOPS and throughput, high cost performance |
For all available device options, see Block Storage devices.
Performance
The key metrics for Block Storage performance are IOPS, throughput, and latency. Some disk types also have capacity constraints — for example, enhanced SSDs (ESSDs) have different capacity ranges depending on the performance level (PL). For specifications across all disk types, see ECS block storage performance.
Data durability and availability
Block Storage stores three copies of your data within the same zone, delivering 99.9999999% (nine 9s) data reliability during read and write operations.
Backup and recovery: Snapshots back up cloud disk data — including logs and transaction records — and support disk restoration and disk image creation. Create snapshots on a regular schedule to protect against accidental deletion or corruption. For an overview, see Snapshot overview.
Scalability
Scale out cloud disk storage using any of the following methods when your data grows:
Resize the disk — Extend the existing disk, then resize or create new partitions.
Add a disk — Create a new cloud disk, attach it to your ECS instance, and partition and format it.
Replace the system disk — Replace the system disk with a larger one.
Security
Access control
Use Resource Access Management (RAM) to grant other users access to your cloud disks with fine-grained permissions.
Encryption
For data-sensitive workloads, encrypt your cloud disks. Encryption and decryption are automatic:
Data is encrypted using AES-256 when it is transmitted from an ECS instance to a cloud disk.
Data is decrypted automatically when read.
Cloud disk snapshots are also encrypted. For an overview, see Encryption overview.
API and management options
Block Storage supports GET and POST requests over HTTP or HTTPS. Manage cloud disks and snapshots programmatically with:
ECS SDKs — Integrate disk management into your applications.
Alibaba Cloud CLI — Run commands from the terminal.
Alibaba Cloud API Explorer — Explore and test API operations in a browser.
Supported operations include: create, delete, query, attach, detach, and scale out cloud disks; create, delete, and query cloud disk snapshots stored in OSS.
To manage Block Storage through a graphical interface, use the ECS console.
Billing
Block Storage supports two billing methods:
| Billing method | Description | Best for |
|---|---|---|
| Pay-as-you-go | Billed by actual usage; activate and release resources at any time | Variable or unpredictable workloads |
| Subscription | Purchase capacity in advance at a lower unit price | Stable, predictable workloads |
Pay-as-you-go costs are 30%–80% lower than traditional hosts. Subscription reduces costs further for predictable usage.
Billing rules for cloud disks
The billing method of a cloud disk depends on how it was created:
Created with an ECS instance — Inherits the billing method of the ECS instance.
Created for a subscription ECS instance — Billed by subscription.
Created on the Disks page of the ECS console — Pay-as-you-go only.
Created from a snapshot — Pay-as-you-go only.
To change the billing method of an existing disk, see Change the billing method of a disk.
Storage capacity units (SCUs) can offset the bills of eligible pay-as-you-go cloud disks in the same region. For details, see SCU overview.
What's next
ECS block storage performance — Performance specifications for cloud disks and local disks.
Snapshot overview — How to back up and restore disk data.
Encryption overview — Disk encryption concepts and setup.
Change the billing method of a disk — Switch between pay-as-you-go and subscription.
SCU overview — Use storage capacity units to reduce costs.