This topic describes the disks used by Edge Node Service.
Overview
Alibaba Cloud disks are block-level data storage resources for ENS. They provide low latency, high performance, high durability, and high reliability. Alibaba Cloud disks use a distributed triplicate mechanism to ensure at least 99.9999% data reliability for ENS instances.
Types of disks
Disks are classified into ultra disks and all-flash disks based on the performance, or system disks and data disks based on the usage.
Dimension | Disk type | Description |
Performance | Ultra disk | Ultra disks are cost-effective disks that provide medium random IOPS and high data reliability. |
All-flash disk | All-flash disks are high-performance disks that provide consistent high random IOPS and high data reliability. | |
Usage | System disk | System disks contain operating systems and can be created only along with ENS instances. The lifecycle of a system disk is the same as that of the instance to which the system disk is attached. |
Data disk | Data disks are used to store application data and can be created separately or along with ENS instances. |
Limits
A disk can be attached to a single ENS instance that resides on the same node as the disk.
Item | Limit |
Maximum number of system disks on an instance | 1 |
Maximum number of data disks on an instance | 15 |
Capacity of an ultra disk | 20 GB to 10 TB |
Capacity of an all-flash disk | 20 GB to 2 TB |
Data security
Read/write stability
Three replicas of your business data are stored in a storage cluster on a node to ensure at least 99.9999% data reliability for ENS instances when read and write operations are performed.
Data deletion mechanism
When you delete data, the data is completely cleared from the distributed storage system and can no longer be accessed by other users. If a disk is released, the storage system destroys the metadata to ensure that the data can no longer be accessed. At the same time, the physical storage space that corresponds to the disk is recycled. The physical storage space must be cleared before it is re-assigned to store data. Before data is written to a new disk, the system returns only zero for all read requests.
Billing methods
Disks that are separately created use the pay-as-you-go billing method. Disks that are created along with ENS instances use the same billing method and have the same lifecycle as the ENS instances to which the disks are attached. The actual prices on the buy page prevail.
Billing method | Description |
Subscription (for disks that are created along with subscription instances) |
|
Pay-as-you-go (for disks that are created separately or along with pay-as-you-go instances) |
|