I just did a little bit of math recently. I did some rough guestimates (counting data elements at the entry level in a CDA document for a healthy patient). I figured that about 20 records (rows in a table) would be needed to store the clinical data for a healthy patient. I know from other work that I've done that for a patient with a chronic condition, a few medications, some allergies and family history and a few other things, that this could climb easily to 100 or even 200. Let's work with healthy patients.
The state of Texas is about 25 million people (round down to the nearest 5 for ease of computation). If the data for every patient in Texas was captured, and all were healthy, and all were stored somewhere, we'd be talking about 20 records/person * 25 million persons = 500 million records.
In simple terms, that's half a billion in one year.
There are around 1.2 billion office visits a year in the US. Each would generate a bit more than one medical summary (I'm guessing less than 1.1). To account for the fact that these patients are health and sick, let's split the difference and call it 50 records per document. That's 66 billion records. Just to be nice, I'll say that each record can fit in 1000 bytes. That's 66 trillion bytes. Collect that data for 10 years. 660 trillion bytes.
How quickly you approach a petabyte.
I'm so glad I don't do imaging.