MongoDB副本集配置系列九：MongoDB 常见问题

• What is a namespace in MongoDB?
• If you remove a document, does MongoDB remove it from disk?
• When does MongoDB write updates to disk?
• How do I do transactions and locking in MongoDB?
• How do you aggregate data with MongoDB?
• Why does MongoDB log so many “Connection Accepted” events?
• Does MongoDB run on Amazon EBS?
• Why are MongoDB’s data files so large?
• How do I optimize storage use for small documents?
• When should I use GridFS?
• How does MongoDB address SQL or Query injection?
  • BSON
  • JavaScript
  • Dollar Sign Operator Escaping
  • Driver-Specific Issues
• How does MongoDB provide concurrency?
• What is the compare order for BSON types?
• When multiplying values of mixed types, what type conversion rules apply?
• How do I query for fields that have null values?
  • Comparison with Null
  • Type Check
  • Existence Check
• Are there any restrictions on the names of Collections?
• How do I isolate cursors from intervening write operations?
• When should I embed documents within other documents?
• Where can I learn more about data modeling in MongoDB?
• Can I manually pad documents to prevent moves during updates?

摘自官网：http://docs.mongodb.org/manual/faq/developers/#what-is-a-namespace