Help Center/ Elastic Volume Service/ User Guide (Ankara Region)/ Overview/ Device Types and Usage Instructions
Updated on 2024-04-15 GMT+08:00
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Device Types and Usage Instructions

What Device Types Are Available?

There are two EVS device types: Virtual Block Device (VBD) and Small Computer System Interface (SCSI).
  • VBD is the default EVS device type. VBD EVS disks support only basic read/write SCSI commands.
  • SCSI EVS disks support transparent SCSI command transmission and allow the server OS to directly access the underlying storage media. Besides basic read/write SCSI commands, SCSI disks support advanced SCSI commands.

Device type is configured during creation. It cannot be changed after the disk has been created.

Common Application Scenarios and Usage Instructions of SCSI EVS Disks

  • Shared SCSI EVS disks: Shared SCSI EVS disks must be used together with a distributed file system or cluster software. Because most cluster applications, such as Windows MSCS, Veritas VCS, and Veritas CFS, require SCSI reservations, you are advised to use shared EVS disks with SCSI.

    SCSI reservations take effect only when shared SCSI EVS disks are attached to ECSs in the same ECS group. For more information about shared EVS disks, see Shared EVS Disks and Usage Instructions.

Do I Need to Install a Driver for SCSI EVS Disks?

To use SCSI EVS disks, a cloud server must have a SCSI driver installed. If the SCSI driver is not pre-installed, you need to install it manually.

Check whether you need to manually install the driver based on the server type.
  • KVM ECS

    You are advised to use SCSI EVS disks with KVM ECSs. Linux images and Windows images for KVM ECSs already have the required driver. Therefore, no driver needs to be installed for KVM ECSs.

    Currently, only KVM ECSs are supported.

  • If neither of the server types are used, you need to manually install the driver on your server.
Parent topic: Overview