Reviewed-by: Miskanin, Jan <jan.miskanin@t-systems.com> Co-authored-by: zhangyue <zhangyue164@huawei.com> Co-committed-by: zhangyue <zhangyue164@huawei.com>
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Constraints
This section describes the constraints on using EVS.
Scenario |
Item |
Restrictions |
---|---|---|
Capacity of a data disk |
|
|
Disk performance |
Common I/O |
|
High I/O |
|
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General Purpose SSD |
|
|
Ultra-high I/O |
|
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Extreme SSD |
|
|
Disk creation restrictions on accounts |
Permission requirement |
The account used to create EVS disks must have the evs:volumes:create permission. For how to add permissions, see EVS Custom Policies. |
Disk creation |
Maximum number of disks that can be created at a time |
100 |
Disk creation from snapshot |
|
|
Disk creation from backup |
|
|
Disk creation from image |
|
|
Device type |
The device type of a disk cannot be changed after the disk has been created. |
|
Disk sharing |
The sharing attribute of a disk cannot be changed after the disk has been created. |
|
Disk encryption |
The encryption attribute of a disk cannot be changed after the disk has been created. |
|
Disk attachment |
Constraints on region and AZ |
The disk and server must be in the same region and AZ. |
Maximum number of servers that a non-shared disk can be attached to |
1 |
|
Maximum number of servers that a shared disk can be attached to |
16 |
|
Maximum number of disks that can be attached to an ECS |
This value varies with ECS types. For details, see section "Can I Attach Multiple Disks to an ECS?" in the Elastic Cloud Server User Guide. |
|
Maximum number of disks that can be attached to a BMS |
60 (1 system disk and 59 data disks) |
|
Device name |
|
|
Disk capacity expansion |
Capacity expansion |
Disk capacity can be expanded, but cannot be reduced. |
Capacity expansion of non-shared disks |
Some server OSs support the capacity expansion of non-shared, In-use disks. For details, see Expanding Capacity for an In-use EVS Disk. |
|
Capacity expansion of shared disks |
A shared disk must be detached from all its servers before expansion. That is, the shared disk status must be Available. |
|
Expansion increment |
1 GiB |
|
Disk detachment |
System disk detachment |
A system disk can only be detached offline, which means that the server must be in the Stopped state. |
Data disk detachment |
A data disk can be detached online or offline, that is, its server can either be in the Running or Stopped state. |
|
Disk deletion |
Deletion of disks |
|
Snapshot |
Maximum number of snapshots that can be created for a disk |
7 |
Snapshot data rollback to disk |
|
|
Tag |
Maximum number of tags that can be added for a disk |
10 |