Data Storage

EVS Disk Types

ECSs support the following types of EVS disks for storing data:

  • Common I/O: EVS disks of this type deliver a maximum of 1,000 IOPS. This disk type is suitable for application scenarios that require large capacity, a medium read/write rate, and fewer transactions, such as enterprises' office applications and small-scale test.
  • Ultra-high I/O: EVS disks of this type deliver a maximum of 20,000 IOPS and a minimum of 1 ms read/write latency. This disk type is excellent for ultra-high I/O, ultra-high bandwidth, and intensive read/write application scenarios. For example, the distributed file systems in the HPC scenarios or NoSQL and relational databases in I/O-intensive scenarios.

EVS disks with different I/O capacities provide different features at different prices. Choose EVS disks based on your requirements. For more information about EVS disk specifications and performance, see Elastic Volume Service User Guide.

EVS Disk Device Types

EVS disks have two device types, Virtual Block Device (VBD) and Small Computer System Interface (SCSI).
  • VBD

    When you create an EVS disk on the management console, Device Type of the EVS disk is VBD by default. VBD EVS disks support only simple SCSI read/write commands.

  • SCSI

    You can create EVS disks for which Device Type is SCSI on the management console. These EVS disks support transparent SCSI command transmission, allowing ECS OS to directly access underlying storage media. SCSI EVS disks support both basic and advanced SCSI commands.


    For more information about how to use SCSI EVS disks, such as installing a driver for a SCSI EVS disk, see FAQs > Do I Need to Install a Driver for EVS Disks with Device Type SCSI? in Elastic Volume Service User Guide.