You can resize disks at any time, regardless of whether the disk is attached to a running instance.
The command for resizing a regional persistent disk is identical to that of resizing a standard persistent disk, however, there is an additional flag for the region.
Resizing a regional persistent disk.
Go to the Disks page.
Select the disk you want to resize.
Click Edit at the top of the page.
Enter the size in GB for the disk.
You can only increase the size of the disk. You cannot decrease a disk's size.
After you resize the disk, you must resize the file system so that the operating system can access the additional space.
The new disk size is displayed in the list of disks.