It can confusing when you have multiple persistent disks on an instance running on Google Compute Engine. For example, a server may have separate disks for the filesystem root, MySQL data, logs, and /tmp. Once you’ve created the Compute Engine disks and attached each one to the instance, how do you know which Compute Engine disk maps to each volume on the instance?
First, describe the instance to see a list of the attached disks:
gcloud compute instances describe my-instance-name ... disks: - autoDelete: true boot: true deviceName: persistent-disk-0 index: 0 interface: SCSI kind: compute#attachedDisk licenses: - https://www.googleapis.com/compute/v1/projects/centos-cloud/global/licenses/centos-7 mode: READ_WRITE source: https://www.googleapis.com/compute/v1/projects/project-name/zones/us-east1-b/disks/disk-01 type: PERSISTENT - autoDelete: false boot: false deviceName: persistent-disk-1 index: 1 interface: SCSI kind: compute#attachedDisk mode: READ_WRITE source: https://www.googleapis.com/compute/v1/projects/project-name/zones/us-east1-b/disks/disk-02
Note the index of each disk. Then, on your instance, list the disks by ID:
ls -l /dev/disk/by-id/ total 0 lrwxrwxrwx. 1 root root 9 Jul 25 19:53 google-persistent-disk-0 -> ../../sda lrwxrwxrwx. 1 root root 10 Jul 25 19:53 google-persistent-disk-0-part1 -> ../../sda1 lrwxrwxrwx. 1 root root 9 Jul 25 19:53 google-persistent-disk-1 -> ../../sdb lrwxrwxrwx. 1 root root 9 Jul 25 19:53 google-persistent-disk-2 -> ../../sdc lrwxrwxrwx. 1 root root 9 Sep 17 14:05 google-persistent-disk-3 -> ../../sdd lrwxrwxrwx. 1 root root 9 Jul 25 19:53 google-persistent-disk-4 -> ../../sde
This listing shows you the volume for each disk that is attached.