Tape is one. But organizations that are forced to deal with increased accessibility and multiple retention periods...
with a long-term archive have found that tape storage has become less feasible. SMBs will likely be deterred from choosing CAS as a media of choice for archiving due to the lack of resources to handle tapes during discovery or investigation and the cost of restoration during a discovery event.
A legal service provider can charge between $500 and $2,000 per tape, depending on the amount of data and the format of that tape for recovery services. Additionally, since tapes are usually used in rotation, there is a risk that they may be accidentally erased when they should be preserved as part of an ongoing legal matter.
Another challenge for long-term data retention with tape is if you have to keep records for 20 years because of HIPAA regulations or 30 years because of OSHA regulations. What are the chances the tape will be even readable by then or that the tape drive format you are using will still work?
There are other platforms that use NFS or CIFS protocols and the right ones read many files for long-term active archives. For example, Hitachi entered the fixed-content archiving department when it partnered with Archivas in 2006 and cemented its commitment when it acquired Archivas in 2007. That platform uses open standards such as NFS and CIFS to access data archives and storage data in standard formats like XML and HTML.
Something else to consider is that while CAS has a mechanism for storing metadata about objects; these NAS devices don't. So you need to make sure that your archiving data can double as your metadata storage if you're using one of these alternative solutions.
So, while there are alternatives, there are pluses and minuses to every approach.
Check out the entire CAS FAQ.