Additional disks to attach to the instance. One disk per line, using comma-separated key=value pairs. Three modes are supported:

1. Create from snapshot (--create-disk) — line contains source-snapshot. Keys: source-snapshot (required), size, type, name, description.
2. Create blank disk (--create-disk) — line contains size or type but no source-snapshot. Keys: size (required), type, name, description.
3. Attach existing disk (--disk) — line contains only name. Keys: name (required).

Common keys (all modes): device-name, mode (ro | rw, default rw), interface (SCSI | NVME), auto-delete (yes | no, default yes).

Examples:

source-snapshot=my-data-snapshot,size=100,type=pd-ssd,auto-delete=yes
size=200,type=pd-ssd,name=scratch-disk,auto-delete=yes
name=shared-data-disk,mode=ro,auto-delete=no

Short names for source-snapshot, type, and name are automatically qualified to the instance's project and zone. For cross-project resources, use a relative path (e.g. projects/{project}/global/snapshots/{name}) or full resource URI (e.g. https://compute.googleapis.com/compute/v1/projects/{project}/global/snapshots/{name}). Mounting disks inside the VM must be done via the startup script.