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FAQ about Pay-As-You-Go cloud disks and zones

Last Updated: Mar 06, 2018

1. What is a zone?

A zone is a physical area within a region that has independent power supplies and network from other areas. Faults are isolated within a zone.

  • ECS instances within the same zone experience lower latency.
  • Different zones within the same region are interconnected on an intranet.
  • Faults are isolated between different zones within the same region.

You can mount and unmount Pay-As-You-Go cloud disks between different ECS instances in the same zone.

2. How should I select a zone based on the requirements of the application on the server?

  • If you need high application availability, we recommend that you create ECS instances in different zones.
  • If you need lower network latency, we recommend that you create ECS instances in the same zone.

You can only mount an independent cloud disk to ECS instances in the same zone.

3. What is the difference between a Pay-As-You-Go cloud disk and a cloud disk?

  • Pay-As-You-Go cloud disks can be unmounted. If you purchase a Pay-As-You-Go cloud disk and mount it to an ECS instance, the Pay-As-You-Go cloud disk is the same as a cloud disk.
  • Cloud disks (including Basic cloud disk, Ultra cloud disk, and SSD cloud disk) are directly generated at the purchase of ECS instances and cannot be unmounted.

4. Are the performance and data security of Pay-As-You-Go cloud disks and Basic cloud disks the same? Is there an improvement on disk performance?

It depends on the type. A cloud disk and Pay-As-You-Go cloud disk of the same type have no difference in terms of disk performance.

5. Can I create a Pay-As-You-Go cloud disk with a custom snapshot?

Yes. Select an existing snapshot to create a Pay-As-You-Go cloud disk. The size and data of the newly created Pay-As-You-Go cloud disk are identical to those of the snapshot, and the size cannot be changed.

6. What is a mount point?

A mount point is the location of the Alibaba Cloud ECS disk on the disk controller bus. The mount point matches the disk device number in Linux, and matches the disk order in the disk manager in Windows.

7. Can I mount one Pay-As-You-Go cloud disk to multiple ECS instances?

No. A Pay-As-You-Go cloud disk can only be mounted to one ECS instance in the same zone, and cannot be mounted across zones.

8. How many Pay-As-You-Go cloud disks can be mounted to one ECS instance?

16 at most, including cloud disks and Pay-As-You-Go cloud disks.

9. Can I mount a Pay-As-You-Go cloud disks to a Subscription or a Pay-As-You-Go ECS instance?

Yes.

10. Why can’t I find my ECS instance when mounting a Pay-As-You-Go cloud disk?

  • Make sure that your ECS instance and the Pay-As-You-Go cloud disk are in the same zone of the same region. Pay-As-You-Go cloud disks can only be mounted within the same zone in the same region.

  • Make sure that your ECS instance has not been released.

11. After I buy a Pay-As-You-Go cloud disk, do I have to perform any extra operations to mount it to the mount point on the ECS instance?

Yes. After mounting your disk successfully, you must log on your ECS instance to perform the Partition Formatting and New Partition Mounting operation on the mounted disk. For more information, see Linux Format and Attach a Data Disk.

12. I have renewed and changed the configuration of the instance. Can I change a Basic cloud disk into a Pay-As-You-Go cloud disk during the instance renewal and configuration period?

No. You can click to renew and change configurations after the period is over to change the Basic cloud disk into a Pay-As-You-Go cloud disk.

13. Why did the automatic snapshot of my Pay-As-You-Go cloud disk disappear?

A Pay-As-You-Go cloud disk implements the new automatic snapshot policy only after being mounted to an ECS instance. Automatic snapshots created earlier will be gradually removed over time.

14. When I reinitialize a disk, will my snapshots be retained?

Yes. Both the manual snapshots and the automatic snapshots will be retained.

15. When I change the system disk, will my snapshots be lost?

The automatic snapshots will be lost, but the manual snapshots will not.

Note: The disk ID will change when you change the system disk, and the custom snapshot of the original system disk cannot be used to roll back the new system disk. However, you can use the user-defined manual snapshot preserved on the original system disk to create a custom image.

16. When I unmount a Pay-As-You-Go cloud disk, will the data on my disk be lost?

In Windows, we recommend that you stop the reading and writing operations on all file systems on the cloud disk to make sure data integrity. Otherwise, the data being read or written will be lost. In Linux, you must log on to the ECS instance and run the umount command for the disk. After the command is executed successfully, log on to the Alibaba Cloud console to unmount the disk.

17. Can I unmount the system disk?

No.

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