Yes. All data is stored redundantly in multiple locations, meaning a catastrophic failure of one server will not result in the loss of your data.
For additional piece of mind, you may choose to download all your project data periodically and back it up on your local servers. You can download your data from the user name menu. Choose "Your Subscription", then click "Download Backup Data."
Photos and other electronic documents are not part of this download. If you want to download documents or photos, you can do so from the documents lists for associated properties. We recommend you keep local electronic copies of all documents and photos you upload to Landscape. You can also download documents in bulk from a documents view. More on that process here.
Historical versions of photos and documents are not kept, but it is possible to get back to earlier versions of your other data if absolutely necessary.