This topic summarizes the common questions encountered in the use of EVS.

Is EVS a network disk?

No.

An EVS disk is usually mounted to elastic cloud servers and dedicated physical servers. Unlike network disks, EVS disks cannot store data alone.

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 to use a newly created EVS?

A newly created EVS disk cannot be used alone and instead, must be mounted to elastic cloud servers and dedicated physical servers.

A newly created EVS disk can be used only after it is mounted in the console and then initialized on the elastic cloud server or dedicated physical server. For more information, refer to:

Mounting EVS

Initializing EVS

Can an EVS disk be used alone?

No.

As a block storage device, an EVS disk, no matter it is used as a system disk or a data disk, must be mounted to an elastic cloud server or dedicated physical server for data storage.

Can a system disk be purchased separately?

eSurfing Cloud automatically creates a system disk based on the operating system selected by the user when creating an elastic cloud server. Users do not need to purchase a system disk separately.

For a data disk, users can purchase one separately, or add multiple data disks when creating an elastic cloud server. For more information, see Creating EVS and Creating ECS.

What are the differences between system disks and data disks?

System disk: an EVS disk used to install the operating system and store the system configuration file in a cloud server. It is similar to drive C in your PC. When purchasing a cloud server, users must also purchase a system disk. Then, the system disk is automatically mounted to the cloud server. A system disk has a maximum capacity of 2048 GB.

Data disk: EVS disks that store data on cloud servers and dedicated physical servers. It is similar to drives D, E, and F in your PC. You can purchase data disks in the following two ways. One is to purchase a data disk when purchasing a cloud server. In this case, the data disk is automatically mounted to the cloud server. The other is to purchase an EVS disk separately in the EVS management console. In this case, you must manually mount the EVS to the cloud server. A data disk has a maximum capacity of 32 TB (32768 GB).

Users can determine the capacity of system disks and whether to purchase data disks based on business needs and budget. If your cloud server carries a small amount of service data and a system disk can meet your needs, you do not need to purchase a data disk. If a large amount of data is processed, we recommend that you purchase a data disk.

What is the maximum capacity of a single EVS?

A system disk has a maximum capacity 2 TB (2048 GB).

The X series data disks have a maximum capacity of 64 TB (65536 GB) and other data disks have a maximum capacity of 32 TB (32768 GB).

The maximum capacity of a single EVS must not be exceeded when you create an EVS disk. For more storage capacity, users can mount multiple EVS disks to a single ECS to scale up the storage space.

How to view the information of purchased EVS disks?

You can view the information of purchased EVS disks in the following two methods:

• Viewing in the EVS management console

• Viewing in the ECS management console

For more information, see Viewing EVS Details.

How is the performance of X Series EVS disks calculated?

Performance per EVS disk = Basic performance + pre-configured performance. The basic performance is calculated based on the basic IOPS formula, and the pre-configured performance is user-defined. For details about the basic IOPS formula, see Specifications of X Series X EVS Disks.

For example, if you order a 100 GB XSSD-2 EVS disk with 1,000 IOPS pre-configured, so the maximum IOPS of the XSSD-2 EVS disk is: (3,000 + 50 × 100) + 1,000 = 9,000. The basic performance is 3,000 + 50 × 100 = 8,000, and the pre-configured IOPS is 1,000.

How can I configure an X series EVS disk with 1 million IOPS?

Firstly, select XSSD-2 as the disk type and set the capacity to 2,000 GB or above.

Secondly, enable the IOPS pre-configuration and configure the IOPS value to the maximum as prompted.

In this way, the maximum IOPS of the EVS disk is set to 1 million.

Is the pay-as-you-go permission required for users to pre-configure IOPS?

Yes. The pay-as-you-go permission is required for pre-configuring the IOPS.

If not granted the pay-as-you-go permission, a user will receive the prompt message reading "Your account balance is less than CNY 100 or the pay-as-you-go feature is not supported. Please try again after confirmation" when purchasing a service. In this case, apply for the pay-as-you-go permission and keep sufficient balance in your account, and then purchase the EVS again.

How to change a non-shared EVS to a shared EVS?

You cannot change the property of a shared EVS once ordered.

If you need a shared EVS, purchase a EVS disk again, and check the "Shared EVS" property when you configure parameters on the Create page to set a shared EVS.

Can I change the disk type after an EVS Disk is created?

Yes.

eSurfing Cloud supports changing the EVS disk type upon the following limitations:

• Currently, only the following two disk type change paths are supported:

Source EVS Disk Type	Target EVS Disk Type That Can Be Changed
Common I/O	High I/O
Generic SSD	Ultra-High I/O

• You can only change the disk type for data disks, not for the system disk.

• You cannot change the disk type for the EVS disks purchased with an ECS.

• The process of changing the disk type is subject to the following limitations:

o Canceling the change is not supported

o EVS snapshots cannot be created

o VBS backups cannot be created

o Capacity expansion is not supported

o Snapshot rollback is not supported

o EVS disks cannot be attached or detached

o Modifying the billing mode (switching between pay-as-you-go and yearly/monthly subscription) is not supported

o Renewal, unsubscription, and deletion are not supported

Can the availability zone of your purchased EVS be changed?

No. You cannot change the availability zone of your purchased EVS. The EVS disk must reside in the same availability zone as the cloud server to which it is mounted.

If you select a wrong availability zone when you purchase EVS disks, you must cancel or delete your subscription and purchase EVS disks again. As a result, select an availability zone with due care when you purchase EVS disks.

How to monitor EVS usage?

Users can monitor EVS usage using the Cloud Eye feature. For more information, see Viewing EVS Monitoring Metrics.. The following are monitoring metrics you can view:

Monitoring Metrics	Metric Description	Measurement Object
Disk read rate	This metric specifies the amount of data read from a measurement object per second. Unit: KB/s	EVS
Disk write rate	This metric specifies the amount of data written into a measurement object per second. Unit: KB/s	EVS
Disk read request rate	This metric specifies the number of requests to read data from a measurement object per second. Unit: IOPS	EVS
Disk write request rate	This metric specifies the number of requests to write data into a measurement object per second. Unit: IOPS	EVS
Average size of write operations	This metric specifies the average number of bytes transmitted per write I/O operation on a measurement object in a measurement period. Unit: KByte/op	EVS
Average size of read operations	This metric specifies the average number of bytes transmitted per read I/O operation on a measurement object in a measurement period. Unit: KByte/op	EVS
Average time of write operations	This metric specifies the average operation duration of each write I/O on a measurement object in a measurement period. Unit: ms/op	EVS
Average time of read operations	This metric specifies the average operation duration of each read I/O on a measurement object in a measurement period. Unit: ms/op	EVS

How to improve the performance of EVS?

Users can use LVM to manage EVS and build RAID arrays for EVS to improve the performance of EVS.

For more information, refer to:

Creating Logical Volume using LVM and Formating File System

Building RAID Arrays using EVS

Can the capacity of a data disk be combined with that of a system disk?

No.

You can expand the capacity of data disks or system disks by Scaling up EVS to increase the storage space.

What are the differences in the partitioning form between MBR and GPT?

Master Boot Record (MBR) and Globally Unique Identifier Partition Table GUID (GPT) are two different forms of disk partitioning. Select an appropriate partitioning form according to disk capacity. The following table shows the differences:

Partitioning Form	Supported Maximum Disk Capacity	Supported Number of Partitions	Partitioning Tool
MBR	2TB	Four primary partitions Three primary partitions and one extended partition	Linux operating system: fdisk tool or parted tool
GPT	18EB (an EVS disk has a maximum capacity of 32 TB)	Unlimited number of partitions	Linux operating system: parted tool

Can data be recovered after EVS is formatted?

No. Data cannot be recovered after EVS is formatted.

We recommend that you Create EVE Snapshot to back up the data on the EVS before formatting. You can execute Snapshot Rollback to recover the data if necessary.

How to build a RAID group using multiple EVS disks?

In eSurfing Cloud, you can build a RAID group using multiple EVS disks to achieve higher performance, better data reliability and availability.

For more information, see Building RAID Arrays using EVS.

What if a message is displayed indicating that EVS resources are sold out when I purchase or expand them?

Multiple availability zones exist in each region. If resources in the current availability zone are sold out, we recommend that you purchase resources from other availability zone.

If only one availability zone is available, you can submit a ticket for customer support.

Elastic Volume Service

General FAQs