ECS | Elastic Block Storage devices & Disks

Block Storage Overview


Update time: 2022-06-06 17:11
Block storage is a block device product provided by Alibaba Cloud for cloud server ECS. It features high performance and low latency, supports random read and write, and meets data storage requirements in most general business scenarios. You can format and set up a file system to use block storage just like a physical hard drive.

block storage type
Alibaba Cloud provides a variety of block storage products for your cloud server ECS, including cloud disks based on distributed storage architecture and local disk products based on local hard disks of physical machines.

Block Storage Type Description Reference Documentation
Cloud Disk ESSD Cloud Disk is an ultra-high-performance cloud disk product based on a new generation of distributed block storage architecture, combined with 25GE network and RDMA technology, a single disk can provide up to 1 million random read and write capabilities and lower single-path latency.
It is recommended to be used in scenarios such as large OLTP databases, NoSQL databases, and ELK distributed logs.

ESSD cloud disk
SSD cloud disk is a high-performance cloud disk product with stable high random read and write performance and high reliability.
It is recommended to be used in scenarios such as I/O-intensive applications, small and medium relational databases, and NoSQL databases.

Cloud Disk Overview
Efficient cloud disk is a cloud disk product with high cost performance, moderate random read and write performance, and high reliability.
It is recommended to be used in scenarios such as development and testing services and system disks.

Cloud Disk Overview
Ordinary cloud disk belongs to the previous generation of cloud disk products and has been gradually discontinued. none
Local disk Based on the local hard disk device on the physical machine (host) where the ECS instance resides, it provides local storage access capability for the ECS instance. Products designed for business scenarios that have extremely high requirements on storage I/O performance and mass storage cost performance. It has the advantages of low latency, high random IOPS, high throughput, and high cost performance.
NOTE The local disk comes from a single physical machine, and the data reliability depends on the reliability of the physical machine, and there is a risk of a single point of failure. It is recommended that you implement data redundancy at the application layer to ensure data availability. You can use a deployment set to deploy several ECS instances involved in a business on different physical servers to ensure high business availability and underlying disaster tolerance.
local disk
Product performance
Different types of block storage have different performance:
For the performance description of cloud disks, see Block Storage Performance.
For the performance description of the local disk, see Local Disk.
Data Security
Note Except for the data erasing mechanism, other contents are only applicable to cloud disks, not local disks.
Read and write stability
In the same Availability Zone, your business data is distributed and stored in the block storage cluster in the form of multiple copies to ensure data stability during reading and writing, and achieve 99.9999999% data reliability guarantee for ECS instances. For more information, see Cloud Disk Three-Copy Technology.

Active backup
You can periodically create snapshots to improve the security of business data. Snapshot is an Alibaba Cloud backup product that provides data backup capabilities for cloud disks, ensuring that information such as logs and customer transactions are backed up for query. For more information, see Snapshots Overview.

data erasure mechanism
The data you delete will not be accessed by other users in any way, and the deleted data in the distributed block storage system will be completely erased. The integrity of data erasure is ensured mainly through the following mechanisms:
The bottom layer of the cloud disk is implemented based on sequential append writing. This design makes full use of the high bandwidth and low latency of sequential writing of physical disks. Based on the feature of additional writing, the operation of deleting the logical space of a cloud disk will be recorded as metadata, and the storage system will ensure that all read operations to this logical space return all zeros. In the same way, your overwrite to the logical space will not immediately overwrite the corresponding space on the physical disk. The storage system implements the overwrite of the cloud disk by modifying the mapping relationship between the logical space and the physical space to ensure that the overwritten data cannot be read. . All remaining data on the physical disk formed by deletion or overwriting will be permanently deleted from the underlying physical disk.

When you release a block device (cloud disk), the storage system immediately destroys the metadata, ensuring that data cannot be accessed any more. At the same time, the physical storage space corresponding to the cloud disk will be reclaimed. Before the physical space is allocated again, it must be cleared. Before data is written for the first time, the read returns of all newly created cloud disks are all zero.

data encryption
For data-sensitive applications, it is recommended that you encrypt the storage device. ECS cloud disk encryption adopts the industry-standard AES-256 algorithm, and uses the key to encrypt cloud disks and cloud disk snapshots. The data transferred from the ECS instance to the cloud disk is automatically encrypted and decrypted when the data is read. For more information, see Encryption Overview.

billing
For the billing methods and billing items for block storage, see Billing Overview and Block Storage Billing.

usage restrictions
For block storage usage limits and quotas, see Block Storage Usage Limits.

For more information, please check the official documentation.

Cloud Disk Overview


Update time: 2022-05-19 14:30
Cloud disk is a block-level block storage product provided by Alibaba Cloud for cloud server ECS. It features low latency, high performance, durability, and high reliability. The cloud disk adopts a distributed three-copy mechanism to provide 99.9999999% data reliability guarantee for ECS instances. Supports automatic replication of your data within the Availability Zone, preventing data unavailability caused by unexpected hardware failures, and protecting your business from the threat of component failures.

Cloud Disk Type
According to performance classification, cloud disks include the following types of products:
ESSD cloud disk: An ultra-high-performance cloud disk product based on a new generation of distributed block storage architecture, combined with 25GE network and RDMA technology, a single disk can provide up to 1 million random read and write capabilities and lower single-path latency. For more information, see ESSD Cloud Disk.
It is recommended to be used in scenarios such as large OLTP databases, NoSQL databases, and ELK distributed logs.

SSD cloud disk: A high-performance cloud disk product with stable high random read/write performance and high reliability.
It is recommended to be used in scenarios such as I/O-intensive applications, small and medium relational databases, and NoSQL databases.

Efficient cloud disk: Cloud disk products with high cost performance, moderate random read and write performance, and high reliability.
It is recommended to be used in scenarios such as development and testing services and system disks.

Ordinary cloud disk: It belongs to the previous generation of cloud disk products and has been gradually stopped selling.
The performance comparison of various types of cloud disks is shown in the following table.

Performance category ESSD cloud disk SSD cloud disk Efficient cloud disk Ordinary cloud disk
PL3 PL2 PL1 PL0
Single disk capacity range (GiB) 1261~32,768 461~32,768 20~32,768 40~32,768 20~32,768 20~32,768 5~2,000
Maximum IOPS 1,000,000 100,000 50,000 10,000 25,000 5,000 Hundreds
Maximum throughput (MB/s) 4,000 750 350 180 300 140 30~40
Single-disk IOPS performance calculation formula min{1,800+50*capacity, 1,000,000} min{1,800+50*capacity, 100,000} min{1,800+50*capacity, 50,000} min{ 1,800+12*capacity, 10,000 } min{1,800+ 30*capacity, 25,000} min{1,800+8*capacity, 5,000} none
Single-disk throughput performance calculation formula (MB/s) min{120+0.5*capacity, 4,000} min{120+0.5*capacity, 750} min{120+0.5*capacity, 350} min{100+0.25*capacity, 180} min{120+0.5*capacity, 300} min{100+0.15*capacity, 140} none
Single-channel random write average delay (ms), Block Size=4K 0.2 0.2 0.2 0.3~0.5 0.5~2 1~3 5~10
API parameter values ​​cloud_essd cloud_essd cloud_essd cloud_essd cloud_ssd cloud_efficiency cloud
For more information about the performance of cloud disks, see Block Storage Performance.

According to the usage classification, cloud disks include system disks and data disks:
The system disk is a cloud disk with an operating system installed. It can only be created with the instance and has the same life cycle as the attached ECS instance.
Data disks are used to store application data and can be created at the same time as the ECS instance or independently.
NOTE When creating a cloud disk, the capacity displayed in the console includes the capacity occupied by the system, and the remaining available capacity may be smaller than the capacity displayed in the console. For example, the console shows that the system disk capacity is 40 GiB, and the system disk needs to occupy a part of the capacity to install the operating system, so the remaining available capacity will be less than 40 GiB.
usage restrictions
A cloud disk can only be attached to one ECS instance in the same region and same availability zone.

For more restrictions, see the table below.

Restrictions Restrictions Ways to increase the limit
User restrictions for creating pay-as-you-go cloud disks Real-name authentication is required to create cloud disks in Mainland China. none
View the resource quota on the ECS management console by the total number of cloud disks. For details, see Viewing and Increasing Resource Quotas. none
Number of single-instance system disks 1 block None
Number of single-instance data disks 64
Note A maximum of 16 data disks can be mounted when an instance is created. If the instance needs more data disks, you need to continue to mount it after the instance is created. The maximum number of cloud disks supported by different instance types is different. For more information, see Instance Type Families.
none
High-efficiency cloud disk capacity quota by volume View the resource quota on the ECS management console. For details, see Viewing and Increasing Resource Quotas. none
Per-volume SSD cloud disk capacity quota View the resource quota on the ECS management console. For details, see Viewing and Increasing Resource Quotas. none
Per-volume ESSD cloud disk capacity quota View the resource quota on the ECS management console. For details, see Viewing and Increasing Resource Quotas. none
A single ordinary cloud disk capacity 5 GiB~2,000 GiB None
Single SSD cloud disk capacity 20 GiB~32,768 GiB None
Single high-efficiency cloud disk capacity 20 GiB~32,768 GiB None
Capacity of a single ESSD cloud disk
PL0: 40 GiB ~ 32,768 GiB
PL1: 20 GiB ~ 32,768 GiB
PL2: 461 GiB ~ 32,768 GiB
PL3: 1,261 GiB ~ 32,768 GiB
none
Single SSD local disk capacity 5 GiB~800 GiB None
Single-instance SSD local disk total capacity 1,024 GiB None
System disk single disk capacity limit
Windows Server: 40 GiB~500 GiB
Red Hat: 40 GiB ~ 500 GiB
CoreOS and FreeBSD: 30 GiB~500 GiB
Other Linux: 20 GiB ~ 500 GiB
none
Whether the local disk instance can mount a new local disk by itself. Not allowed. none
Whether the local disk instance supports configuration changes? Only bandwidth changes are allowed. none
System disk mount point range /dev/vda None
Data disk mount point range /dev/vd[b-z] None
billing
For the specific price information of cloud disks, please refer to the ECS product details page of the cloud server.

The cloud disk supports two billing methods: annual subscription and pay-as-you-go. For details, see Annual subscription and pay-as-you-go.

The cloud disk created with the annual subscription instance, or the cloud disk created separately for the annual subscription instance, adopts the annual subscription and monthly billing method.
The cloud disk created with the pay-as-you-go instance and the cloud disk created separately are billed on a pay-as-you-go basis. Among them, the storage capacity unit package you purchased can be automatically deducted from the pay-as-you-go bill of the cloud disk.
After creating a cloud disk, you can switch the billing method of the cloud disk as needed. For details, see Converting Cloud Disk Billing Methods.

For more information, please check the official documentation.

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