# Why Do Some of My EVS Disks Not Have WWN Information?

EVS disks have two device types: VBD and SCSI. WWNs are used as the unique identifiers for SCSI EVS disks, and VBD EVS disks do not have WWNs.

You can view the WWN of a SCSI EVS disk on the management console. The details are as follows:

- If the SCSI EVS disk is brand new, you can view the disk WWN on the disk details page.
  Figure 1 shows the query result.
  Figure 1 Queried WWN information
- If the SCSI EVS disk was created before the WWN feature rollout, the disk WWN will fail to be obtained.

  Figure 2 shows the query result.

  Figure 2 No WWN information

Parent topic: General