What Are the Applicable Scenarios for Different Cloud Disks?
- After purchasing a CVM, if you find that the disk space is insufficient, you can purchase and attach an elastic cloud disk as a data disk to meet storage needs.
- When purchasing a CVM, if you do not want to buy additional data disks, you can purchase an elastic cloud disk when you have storage needs and attach it as a data disk.
- Server A has 10 GB of important data stored in an elastic cloud disk. When the data needs to be shared with server B, the disk can be directly detached from server A and then attached to server B.
- When a single cloud disk with the maximum specification cannot meet storage needs, you can purchase multiple cloud disks of the same capacity and configure an LVM logical volume to provide larger disk space.
- When the I/O performance of a single disk cannot meet the business requirements, you can purchase multiple cloud disks and configure Raid 0 and Raid 10 to improve the I/O performance.
How to Choose a Cloud Disk Type?
Before selecting the type of hard disk, confirm what type of work data you need to store:
- For scenarios with relatively infrequent requests, such as system logs, enterprise work files, data repositories, small blogs, and BBS, we recommend using an HDD cloud disk to reduce costs.
- For common scenarios such as small and medium-sized databases, Web/App applications, and transactional workloads, we recommend you to use Premium Disks for better cost-effectiveness.
- For scenarios with high workload and high performance requirements, such as large core databases, OLTP business, and NoSQL databases, we recommend you to use a Cloud SSD for higher performance.
What Are the Must-Knows for Using Cloud Disks?
- For an independently purchased cloud disk, when configuring static file system information using fstab, you should use the file system's UUID or label as the file system identifier to prevent the kernel name of the cloud disk in the CVM from changing due to repeated attachments and detachments of multiple cloud disks on the same CVM.
- If a cloud disk expires before the CVM does, then that cloud disk will be throttled, detached, or even recycled within a certain period after expiration. Renew the cloud disk in time to prevent impact on your business.
- If detaching a cloud disk from the CVM does not seriously affect your critical business, you can consider using the nofail option when configuring fstab to prevent errors during system reboot caused by cloud disk detachment from the CVM.
- We recommend that you execute the command san policy=OnlineAll in diskpart before using a cloud disk in the Windows operating system.
- When detaching a cloud disk from the Windows operating system, we recommend that you interrupt all read-write operations to the disk first and perform an offline operation.
How to Automatically Mount the Data Disk When Starting a New Instance Using Custom Image and Data Disk Snapshot?
For specific operations, see the Auto Attachment section in Attaching Cloud Disks.
How to Purchase a Cloud Disk?
You can create a cloud disk in the console or via API. For specific operations, see Creating a Cloud Disk.
Why Do I Fail to Find the CVM I Want to Attach to When Attaching a Cloud Disk?
Cloud disks cannot be attached across availability zones. Ensure that your CVM instance and cloud disk are in the same availability zone of the same region, and that your CVM has not been released.
Why Do I Fail to See the New Disk Space in the CVM's Operating System After Attaching a Cloud Disk?
Some Linux CVMs may not be able to recognize the elastic cloud disk. First, you need to enable the disk hot plug feature in the CVM. For details, see Enabling Hot-Swappable Disk Feature.
After manually attaching a cloud disk, you need to select and perform the corresponding subsequent operations to make it available.
| Creation Model | Subsequent Operations |
|---|---|
| Create | - Cloud disk with a capacity of less than 2 TB: Initializing cloud disks (< 2 TB) - Cloud disks with a capacity of greater than or equal to 2 TB: Initializing cloud disks (≥ 2 TB) |
| Creating from Snapshot | - Cloud disks with a capacity that equals the snapshot capacity: No further operations are required. The cloud disk can be used directly after being attached. - Cloud disks with a capacity that is greater than the snapshot capacity and less than or equal to 2 TB, or cloud disks with a capacity that is greater than the snapshot capacity, with the snapshot capacity greater than 2 TB: - Mount to Windows CVM: scale out the partition and file system (Windows) - Mount to Linux CVM: scale out the partition and file system (Linux) - Cloud disks with a capacity of greater than 2 TB, with the snapshot capacity less than or equal to 2 TB: - If MBR partition is used in the snapshot: See Initializing Cloud Disks (≥ 2 TB) to repartition using GPT. This operation will delete existing data. - If the GPT partition is used in the snapshot: - Mount to Windows CVM: scale out the partition and file system (Windows) - Mount to Linux CVM: scale out the partition and file system (Linux) |
After Attaching a Cloud Disk, How to Partition and Format It?
For specific operations, see Initializing Cloud Disks (< 2 TB) or Initializing Cloud Disks (≥ 2 TB).
Is Multiple CVMs Accessing the Same Cloud Disk Supported?
Not supported currently. You can attach up to 20 cloud disks to the same CVM, but currently, multiple CVMs cannot share the same cloud disk simultaneously. Data sharing can only be achieved by detaching the cloud disk from CVM A and then attaching it to CVM B.
When Multiple Cloud Disks of the Same Size and Type Are Attached to the Same CVM, How Can I Distinguish Them in the Operating System?
For a Linux operating system, you can execute the following command to view the correspondence between elastic cloud disks and device names:
ls -l /dev/disk/by-id
For the Windows operating system, you can view it by executing the following command:
wmic diskdrive get caption,deviceid,serialnumberor
wmic path win32_physicalmedia get SerialNumber,Tag
When I Detach a Cloud Disk, Will Data Be Lost?
Data on a cloud disk does not change due to attachment or detachment. To maintain data consistency, we strongly recommend:
- Under the Linux operating system, log in to the CVM instance and umount the disk. After the command is successfully executed, go to the console to unmount the disk.
- Under the Windows operating system, pause the read and write operations of all file systems on this disk before unmounting; otherwise, the data that has not been read or written will be lost.
How to Detach an Elastic Cloud Disk?
For specific operations, see Detaching a Cloud Disk.
After a Cloud Disk Is Successfully Purchased, Can Its Capacity Be Adjusted?
Yes. Cloud disk capacity can be adjusted, and it can be expanded, but not reduced.
What Are the Conditions for Scaling-out the File System?
Only cloud disks can be expanded. Local disks cannot be expanded. For specific operation instructions, see Introduction to Scaling Scenarios.
Note:
- It is strongly recommended that you take a snapshot before the scale-out to ensure data security.
- If the maximum capacity of a cloud disk still cannot meet your business needs, you can use multiple elastic cloud disks to build a RAID group or an LVM logical volume.
- MBR partition supports a disk with a maximum capacity of 2 TB. If you need to extend for over 2 TB, we recommend you create and attach a new data disk and use the GPT partition format.
How to Expand a Cloud Disk?
For a specific operation guide, see Introduction to Scaling Scenarios.
Does the CVM Support CPU/Memory Scale-out?
When the system disk is a cloud disk, the CVM supports CPU and memory adjustments.
What Should I Do If the Cloud Disk Partition Is in MBR Format and Cannot Be Expanded Further?
MBR partition supports a disk with a maximum capacity of 2 TB. If you need to extend for over 2 TB, we recommend you create and attach a new data disk and use the GPT partition format.
What Should I Do If the Cloud Disk Has Been Expanded to Its Maximum Capacity but Still Cannot Meet the Business Needs?
We recommend that you use multiple elastic cloud disks to build an LVM logical volume.
How to Build LV in LVM with Multiple Elastic Cloud Disks?
For specific operations, see Building a Logical Volume in LVM with Multiple Elastic Cloud Disks.
What Happens to the Data When a CVM Is Terminated?
- The lifecycle of the system disk completely follows that of the CVM. When the CVM is destroyed, the data stored in the system disk will also be terminated.
- The lifecycle of a data disk (that is, an elastic cloud disk) is independent of the CVM. You can freely choose whether to retain the elastic cloud disk and its data beyond the lifecycle of the CVM.
Therefore, we recommend that you use an elastic cloud disk to store data that needs to be retained for a long time.
How to Recover a Cloud Disk after It Is Formatted?
The data on a cloud disk cannot be recovered after it is formatted. We recommend that you first create a snapshot before formatting it.
How to Delete a Cloud Disk?
- The lifecycle of the system disk follows that of the CVM and can only be deleted when Terminating Instances.
- The lifecycle of a data disk (that is, an elastic cloud disk) is independent of the CVM and can be deleted independently. For specific operations, see Terminating a Cloud Disk.
Can the System Disk Be Partitioned?
The system disk does not support partitioning.