A Data safe is a special type of safe all its own. These safes, also called media safes have different requirements than other fire safes. The interior temperature must remain lower than a standard fire safe to protect items that melt such as plastic. Plastic is one of the main components in data and media like hard drives, thumb drives, CDs, DVDs, tapes and nearly all other storage medium. This type of safe will keep the inside of the safe below 125 Degrees F and will protect the contents of the safe.
You will find that some data and media safes are rated bu the UL (Underwriters Laboratory), but most are not. The UL rated media safes are higher priced, of very high quality and have been tested for the stated period of and the stated temperature. I highly suggest going with a UL rated model if your budget allows. Most insurance companies will require a UL rating in order to insure the contents of the safe. Check with your insurance company to see what may be required.
There are also smaller data chests that generally are much lower in price and only made to handle small amounts of data. There are media safes that are made to be placed inside another fire safe that are also lower in price and a great deal if you have a fire safe with some extra room. Recently SentrySafe came out with a media safe with built in hard drive.
Data and media safes are made by Cobalt, SentrySafes, Schwab and Fire King. The higher end UL rated models are the Schwab Data Safes and Fire King Media Safes.