Latest Update: Full-data Sandbox is now available for all DCs.An entire replica of your production data with no limits on the number of records copied from modules.
The ability to test automations and performance on a realistic scale.
A proper simulation of your production environment to make testing truly impactful.
How does it work?
On the Sandbox page, click Create New Sandbox.
In the Create New Sandbox pop-up:
Enter a name for the Sandbox.
Provide a brief description of the sandbox.
Select your sandbox type: Full-data sandbox.
Choose your configuration and grant access to your sandbox users. 

Full-data sandbox availability: Available exclusively to organizations on the Ultimate or CRM Plus editions with up to 10GB of storage. For organizations exceeding the 10GB limit, a storage purchase option for full-data sandboxes will be introduced soon.
Rebuild interval: The full-data sandbox can be rebuilt every 30 days.
Sandbox limit: Each organization using the Ultimate or CRM plus editions is allowed to create one full-data sandbox.
Experience unparalleled flexibility and accuracy now in your testing with the new full-data sandbox!
Help resource: Creating Sandbox
Thank you!