I worked at a storage company and it sucked immensely.
Basically data is stored on large hard drives which are attached to servers.
In addition they attempted to have a clever scheme for data integrity/security/recovery etc.
Hard drives are dirt-cheap, but they are very likely to die within 5 years. So, how do you keep the data safe?
Google came up with this back in 2003:
The company that I worked for never got even close. As the result hospitals lost important documents, CIA lost track of terrorists, banks lost customer data - I exaggerate not!
I highly recommend reading the Google File System paper. They did a good job at explaining stuff.
Also, be able to compare different file systems (at a high level): ext3, ext4, reiserFS, NTFS, the one that Apple uses ...
Also try to learn what a company Akamai does and why they are in business - who would pay them and why.
Knowing something about networking, caching, proxy servers, BGP tables http://en.wikipedia.org/wiki/Border_Gateway_Protocol would help.
Look up what the company does, try to figure out who their customers are, what problem they have and why they pay $$$ to your employer. Then try to imagine what low-level details are involved in streaming stuff from point A to point B, including protocols, etc.
Hopefully this will help you 'WOW' them.
Do not be cocky at the interview, even if you happen to know some things that they do not, do not show off. You are trying to get a job, right?
I realize that my answer is not complete, albeit somewhat popular.
I would add knowing the difference between TC and UDP, and when you would need each one.