As any technology, there is always some tradeoff. You gain something while you give up some other things. Online storage do have some attraction.
1. Some initial investment
2. Highly expandable
3. Less technical skill require
4. Available anywhere in the world.
1. Eventhough you have the online storage, you still
need you own backup copy.
2. Sensitive data may/may not be well protect. It all depend on the value of your data to others. If something happen to your data, it is very hard to
prove the data is leak from the vendor.
3. Access speed may not be as good as local storage.
For data replication, better use commerical software. You may try:
They provide active-active replication, which enable both of your site to read/write/modify data
at the same time.