It's true, we also experienced data loss (several millions of log data caused by dirty shutdown, it's data file is very fragile) issue like this thread http://g

It's true, we also experienced data loss (several millions of log data caused by dirty shutdown, it's data file is very fragile) issue like this thread http://groups.google.com/group/mongodb-user/browse_thread/thread/d0111a47984cb688 http://groups.google.com/group/mongodb-user/browse_thread/th... I found the following two posts very insightful： 1, http://www.mikealrogers.com/2010/07/mongodb-performance-durability/ http://www.mikealrogers.com/2010/07/mongodb-performance-dura... "This (mongodb's write plolicy) is kind of like using UDP for data that you care about getting somewhere, it’s theoretically faster but the importance of making sure your data gets somewhere and is accessible is almost always more important." 2, http://www.paperplanes.de/2011/1/10/mongodb_and_data_durability.html http://www.paperplanes.de/2011/1/10/mongodb_and_data_durabil... "It's okay to accept trade-offs with whatever database you choose to your own liking. However, in my opinion, the potential of losing all your data when you use kill -9 to stop it should not be one of them, nor should accepting that you always need a slave to achieve any level of durability. The problem is less with the fact that it's MongoDB's current way of doing persistence, it's with people implying that it's a seemingly good choice. I don't accept it as such."