This section provides guidance on managing shared EVS disks, including usage scenarios, mounting, deletion, and more.
Creating a Shared EVS Disk
When creating a shared EVS disk, users can select either the VBD or SCSI type:
Shared VBD EVS Disk: The default option; does not support SCSI reservations.
Shared SCSI EVS Disk: Supports SCSI reservations.
Mounting a Shared EVS Disk
Unlike a regular EVS disk, which can be mounted to only one ECS, a shared EVS disk can be mounted to up to 16 ECSs simultaneously.
The SCSI EVS disk supports SCSI reservations. To enhance data security, it is recommended to use SCSI reservations combined with the anti-affinity policy of an ECS group. That is, mount shared SCSI EVS disks to ECSs in the same anti-affinity ECS group. If an ECS does not belong to an anti-affinity ECS group, avoid mounting shared SCSI EVS disks, as this may cause SCSI reservations to malfunction, leading to potential data risks.
SCSI Reservation and Anti-affinity ECS Groups
SCSI Reservation: SCSI reservations are implemented using SCSI reservation commands. When an ECS issues a SCSI reservation command to an EVS disk, the disk is locked, preventing reads/writes by other ECSs. This mechanism helps avoid data corruption.
Anti-affinity ECS Group: The anti-affinity policy of an ECS group allows ECSs to be created on different hosts.
For details, see Mounting an EVS Disk > Mounting a Shared EVS Disk.
Deleting a Shared EVS Disk
Since a shared EVS disk is often mounted to multiple ECSs, ensure that it is unmounted from all servers before deletion.
For details, see Deleting an EVS Disk.