Data stored in the memory than easy to understand in the db, not split object, the speed is much faster,
Personal humble opinions on the db before or based on the amount of data to make a evaluation,
Memory so big now, fools think forecast 32 g the following the amount of data (32 gb in east about 500 yuan is a dog, even for a small business is not expensive)
Can not completely DB,
One-time loading when you can start the program, it is good to write back, at the end of a 32 g DB, is sufficient for most small applications,

If consider program may collapse, can open a separate process/machine as a backup, or as a data provider, or as a backup,
But it is different from the DB, this process opens, closing at once the read/write all objects, middle takes any write operations from the "business process" and synchronization to their backup,
Each write operation during this time the whole system, which USES the most stupid way, write three master 2 (1) back again, also much faster than writing a disk,
At the end of the day, when we consider the application architecture, many ignored problems when the size of the small program should be small and fast method,