This topic summarizes the common questions when mounting and unmounting EVS.

How to add data disks to a cloud server?

You can add data disks to a cloud server using the following two methods.

• If you purchase data disks when purchasing a cloud server, data disks will be automatically mounted to the cloud server.

• Create EVS in the EVS console and mount it to the cloud server. Users can mount EVS by selecting the EVS tab on the cloud server details page, or selecting the cloud server from the EVS list. For more information, see Creating EVS and Mounting EVS.

Can EVS disks of different types be mounted to the same cloud server?

Yes.

By default, a cloud server can be mounted with a maximum of nine EVS disks (one system disk and eight data disks). To mount more than nine EVS disks, please contact eSurfing Cloud customer support and submit a ticket for quota increase. A maximum of 23 EVS disks can be mounted.

You can mount EVS disks of different types to the same cloud server. But the EVS disks must be in the same availability zone in the same region with the cloud server.

Can an EVS disk be mounted to multiple cloud servers?

Yes.

When an EVS disk is used as a data disk, you can configure it as a shared EVS. A shared EVS be mounted to multiple cloud servers. For more information, see Managing Shared EVS.

However, the shared EVS must be used in a cluster management environment. The sharing function becomes unavailable if you directly mount the shared EVS to multiple cloud servers and data may be overwritten. Scalable File Service is recommended for data sharing between cloud servers, and Object-Oriented Storage is recommended for data sharing across regions and availability zones.

How many EVS disks can be mounted to a cloud server?

By default, nine EVS disks (one system disk and eight data disks) can be mounted. To mount more than nine EVS disks, please contact eSurfing Cloud customer support and submit a ticket for quota increase. A maximum of 23 EVS disks can be mounted.

A newly created data disk cannot store data directly when mounted to a cloud server. You need to firstly initialize the data disk by creating partitions and formatting the data disk. For more information, see Initializing Data Disk.

Can an EVS disk be mounted across regions or availability zones?

No.

An EVS disk cannot be mounted across regions or availability zones, but can only be mounted to cloud servers or dedicated physical servers in the same availability zone in the same region.

If your EVS resides in the availability zone different from that of the cloud server, we recommend that you:

• Delete or unsubscribe from the EVS, and then purchase an EVS disk in the same availability zone as the cloud server, if the EVS has no data or you no longer need the data in the disk. For more information on how to unsubscribe from EVS, see Unsubscribing from Data Disks in Yearly/Monthly Subscription Mode - EVS.

• Create a VBS for EVS and create a new EVS from the backup, then select the availability zone where the cloud server resides when configuring the information of the EVS, if you want to retain the data in the EVS. It should be noted that VBS can be created across availability zones but not across regions. For more information, see Creating VBS and Creating EVS from
Backup.

Why can't I find the ECS instance to which you want to mount the EVS?

Make sure that your cloud server instance is not released and that the instance and EVS are in the same availability zone in the same region.

In addition, ensure that the EVS to mount and cloud server meet the following prerequisites:

• By default, a cloud server can be mounted with a maximum of nine EVS disks (one system disk and eight data disks). To mount more than nine EVS disks, please contact eSurfing Cloud customer support and submit a ticket for quota increase. A maximum of 23 EVS disks can be mounted.

• Fast SSDs can only be mounted to general-purpose computing-plus and memory-optimized cloud servers with at least 16 vCPUs and later than generation 6, and a maximum of three fast SSDs can be mounted to a cloud server.

• If an EVS disk is not a shared EVS, it can only be mounted to one cloud server.

• If an EVS disk is a shared EVS, it can be mounted to a maximum of 16 cloud servers.

Can the EVS purchased with the cloud server be mounted to another cloud server?

No.

The EVS purchased with the cloud server belongs to the same order and cannot be mounted to another cloud server.

To mount the EVS to another cloud server, we recommend that:

You create a snapshot for the EVS and create a new data disk from the snapshot. The new data disk contains the same data as the source EVS. You can mount the new data disk to another cloud server. For more information, see Creating EVS from Snapshot.

Can a shared EVS be mounted to cloud servers with different operating systems?

You are advised not to mount a shared EVS to cloud servers with different operating systems. The file sharing function becomes unavailable when a shared EVS is directly mounted to multiple cloud servers with different operating systems. The reason is that cloud servers do not agree on data read and write rules. As a result, cloud servers may interfere with each other when reading and writing data, or unexpected errors may occur, such as file corruption, file loss, or read and write inconsistency.

Scalable File Service is recommended for data sharing across operating systems.

Can a shared EVS be mounted to cloud servers under different accounts?

No.

A shared EVS can only be mounted to cloud servers in the same region and availability zone under the same account.

We recommend that you mount a shared EVS to a cloud server group with the same anti-affinity to improve service reliability. In addition, we recommend that you use the SCSI locking mechanism, that is, mounting a shared EVS of SCSI type to a cloud server group with the same anti-affinity to improve service data security.

Must a cluster be set up to use EVS disks?

Yes.

A shared EVS must be used in a cluster management environment, which is determined by the working principles of the EVS and user requirements.

The file sharing function becomes unavailable when a shared EVS is directly mounted to multiple cloud servers or dedicated physical servers. The reason is that cloud servers do not agree on data read and write rules. As a result, cloud servers may interfere with each other when reading and writing data, or unexpected errors may occur, such as file corruption, file loss, or read and write inconsistency.

A shared EVS does not have cluster management capabilities. Therefore, you need to set up a cluster system to share data, such as the Windows MSCS cluster, Veritas VCS cluster, and CFS cluster commonly used in enterprise applications.

Which ECS instances can the fast SSDs be attached to?

The constraints on attaching a fast SSD to an ECS include:

• Fast SSDs can only be attached to general-purpose computing-plus and memory-optimized ECSs with at least 16 vCPUs newer than Generation 6.

• A maximum of three fast SSDs can be attached to an ECS.

• The ECS to which the fast SSD is attached must reside in the same region or AZ.

Can a data disk be retained when the cloud server is unsubscribed or deleted, and then mounted to another cloud server?

If a data disk is purchased with the cloud server, it cannot be separately unmounted or retained.

If the data disk is separately purchased and mounted to the cloud server, the EVS will be automatically unmounted when the cloud server is unsubscribed or deleted, and the EVS and data are still retained. The EVS can then be mounted to other cloud servers in the same availability zone in the same region. It should be noted that if the EVS needs to use the original data after it is mounted again, do not initialize it; otherwise, the original data will be cleared.

What shall I do if a Linux-based EVS is mounted to a Windows operating system?

We do not recommend that you mount the EVS unmounted from the Linux-based cloud server again to a Windows-based cloud server, and vice versa.

Otherwise, the disk may not be correctly displayed due to different formats of the file system. You can format the disk or create partitions if the disk cannot be displayed. Disk formating will lead to data loss. Please create a backup for the EVS in advance to prevent data loss.

Can the data disk purchased with the cloud server be unmounted?

No.

Data disks may be purchased with a cloud server or independently created. The unmounting procedure differs for the two data disks. Data disks purchased with a cloud server cannot be unmounted independently, and independently created data disks can be manually mounted or unmounted to/from a cloud server.

In addition, when the cloud server is deleted or unsubscribed, the data disks ordered with the cloud server will also be deleted/unsubscribed. Independently created data disks mounted on the cloud server will be automatically unmounted. You can manually delete/unsubscribe from the EVS if you no longer need it.

Will data be lost when an EVS disk is unmounted?

Data will not be lost when an EVS disk is unmounted, but it depends.

• When a non-encrypted EVS is unmounted, data will not be lost, and the unmounted EVS can be mounted again. For more information on how to unmount the EVS, see Unmounting EVS

• When an encrypted EVS is unmounted, data will not be lost if the master key is normal and available.

• When an encrypted EVS is unmounted, partial data may be lost if the master key is disable or deleted. Long-term read & write process becomes impossible when the master key is disabled or deleted. In this process, the data may be lost. At the same time, the EVS unmounted in this state cannot be mounted again. As a result, users must be aware of the key state before unmounting the EVS. Do not unmount the EVS when the key is abnormal. You can unmount the EVS after the key resumes normal.

• Before unmounting an EVS mounted to a Windows-based cloud server, ensure that no program is reading or writing data from/to the EVS. Otherwise, data loss may occur or unmounting may fail.

• Before unmounting an EVS mounted to a Linux-based cloud server, log in to the cloud server, run the umount command, and ensure that no program is reading or writing data from/to the EVS. Otherwise, data loss may occur or unmounting may fail.

Why cannot EVS disks be unmounted?

System disks and data disks purchased with a cloud server cannot be unmounted, and independently purchased disks can be mounted.

You can unmount a data disk online or offline. That is, you can unmount the data disk when the cloud server to which the disk is mounted is shut down or running.

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Mounting and Unmounting FAQs