Block Storage is a high-performance, low-latency block storage service that is provided by Alibaba Cloud for Elastic Compute Service (ECS). Block Storage supports random reads and writes to meet your data storage requirements in most common business scenarios. You can use block storage devices in the same manner that you use physical hard disks. You can format block storage devices on ECS instances and create file systems for the devices. This topic describes the categories of block storage devices and how to use block storage devices.
Categories of block storage devices
Alibaba Cloud provides various block storage devices for ECS, including cloud disks that are based on a distributed storage architecture and local disks that are physically attached to physical machines.
Category | Description | References | |
Cloud disks | ESSD AutoPL disks | You can configure provisioned performance and burst performance for ESSD AutoPL disks based on your business requirements. ESSD AutoPL disks inherit the features and performance of enhanced SSDs (ESSDs) and are capable of decoupling disk capacity from disk performance. We recommend that you use ESSD AutoPL disks in the following scenarios:
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ESSDs | ESSDs use a next-generation distributed block storage architecture and support 25 Gigabit Ethernet networks and Remote Direct Memory Access (RDMA). Each ESSD has low one-way latency and can deliver up to 1,000,000 random read/write IOPS. We recommend that you use ESSDs in scenarios such as OLTP databases, NoSQL databases, and ELK distributed logs. | ||
ESSD Entry disks | ESSD Entry disks provide enterprise-grade features and data protection capabilities. We recommend that you use ESSD Entry disks as system disks or in scenarios such as development and testing. Note You can attach ESSD Entry disks to only instances of the u1 and e instance families. For information about the instance families, see the u1, universal instance family section in the "Universal instance families" topic and the e, economy instance family section in the "Shared instance families" topic. | ||
Standard SSDs | Standard SSDs are high-performance disks that provide consistent high random IOPS and high data durability. We recommend that you use standard SSDs in scenarios such as I/O-intensive applications, small and medium-sized relational databases, and NoSQL databases. | ||
Ultra disks | Ultra disks are cost-effective disks that provide medium random IOPS and high data durability. We recommend that you use ultra disks as system disks or in scenarios such as development and testing. | ||
Basic disks | Basic disks are previous-generation disks and are no longer available for purchase. | None | |
Local disks | Local disks reside on the physical machines (hosts) that host ECS instances and provide the instances access to on-premises storage. Local disks are suitable for business scenarios that require high storage I/O performance, a large amount of storage capacity, and high cost-effectiveness. Local disks provide low latency, high random IOPS and throughput, and high cost performance. Note All local disks of an ECS instance reside on a single physical machine. This increases single point of failure (SPOF) risks. The durability of the data that is stored on a local disk is determined by the reliability of the associated physical machine. To ensure data availability, we recommend that you implement data redundancy at the application layer. You can use deployment sets to distribute ECS instances across multiple physical machines for high availability and disaster recovery purposes. |
Performance of block storage devices
Different block storage devices deliver different performance.
For information about the performance of cloud disks, see Block storage performance.
For information about the performance of local disks, see Local disks.
Data security
The following features, except for the data erasure mechanism, are available on cloud disks and unavailable on local disks.
Data durability during read and write operations
Three copies of your business data are stored in a block storage cluster within the same zone to ensure 99.9999999% (nine 9's) data durability during read and write operations. For more information, see Triplicate storage.
Proactive backup
You can create snapshots for disks on a regular basis to enhance data security. Snapshots are a backup service that is provided by Alibaba Cloud. Snapshots back up the data that is stored on disks and ensure that data, such as logs and customer transaction data, can be queried. For more information, see Overview of snapshots.
Data erasure mechanism
When you delete a piece of data, the data is completely erased from the distributed block storage system and can no longer be accessed by other users. The following mechanisms ensure that deleted data is completely erased:
The storage system performs sequential writes to append data to existing files at the underlying layer of cloud disks. This mechanism fully utilizes high-bandwidth and low-latency sequential writes to physical disks. If you delete a logical space from a cloud disk after data is appended at the underlying layer of the cloud disk, the delete operation is recorded as metadata. The storage system returns only zeros for all data read requests from the logical space. Similarly, when you overwrite the data that is stored in the logical space of a cloud disk, the storage system does not immediately overwrite the data in the corresponding physical space. Instead, the storage system modifies the mapping between the logical space and the physical space. This ensures that data that is already overwritten is no longer readable. Data fragments that result from delete or overwrite operations are forcefully and permanently deleted from the underlying physical disks.
When you release an Elastic Block Storage (EBS) device (cloud disk), the storage system immediately destroys the metadata of the device to ensure that the disk data is no longer accessible. At the same time, the physical storage space of the disk is recycled. The physical storage space must be cleared before it is re-assigned. Before data is written to a new cloud disk, the system returns only zeros for all read requests.
Data encryption
If your applications are data-sensitive, we recommend that you encrypt the storage devices that you use. Cloud disks and their snapshots are encrypted by using keys based on the industry-standard AES-256 algorithm. Data is automatically encrypted when it is transmitted from ECS instances to cloud disks. Encrypted data is automatically decrypted when it is read. For more information, see Encryption overview.
Billing
For information about the billing methods and billable items of Block Storage, see Billing overview and Block storage devices.
Limits
For information about the limits and quotas of block storage devices, see the Block storage limits section in the "Limits" topic.
Operations
The following figure shows the common operations that you can perform on a cloud disk during the cloud disk lifecycle.
Phase | Scenario | Operation |
Creation phase | Create an empty cloud disk or a cloud disk that contains data from a snapshot for an ECS instance. |
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O&M phase | View the basic information and monitoring data of a cloud disk. | |
Use the snapshot feature to back up and restore data for a cloud disk. | ||
Upgrade the specifications of a cloud disk to meet your business requirements. | ||
Extend the storage capacity of a cloud disk to meet your capacity requirements. | ||
If you want to restore a cloud disk to its initial state, you can initialize the disk. | ||
If you want to use a new operating system, you can change the operating system of an instance by replacing the system disk. | ||
Release phase | If you no longer need a cloud disk, you can release the disk to reduce costs. |
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You can create and release local disks only together with instances of specific instance types. For more information, see Local disks.
Other Alibaba Cloud storage services
Object Storage Service (OSS) and Apsara File Storage NAS are storage services provided by Alibaba Cloud in addition to Block Storage. For more information, see What is OSS? and What is NAS?