Persistent disk is the term used by Google to identify block storage. It can either be Hard Disk Drive (HDD) or Solid State Drive (SSD). They can be used as non-volatile storage for GCE VMs.
Persistent disks and local SSDs – block storage for GCE
Understanding persistent disks and local SSDs
Standard HDD persistent disks are efficient and economical for handling sequential read/write operations, but are not optimized to handle high rates of random input/output operations per second (IOPS).
If your applications require high rates of random IOPS, use SSD persistent disks. Persistent disks can be attached to multiple instances in read-only mode for data sharing.
One might get confused between Persistent Disks and Cloud...
