...

• MongoDB structure has limitations in number of levels and document size.
  
  • server may have many DBs
  • DB is a container for collections
  • collection is a group of documents
  • document is a JSON/BSON object of key:value pairs (dictionary). Each value may be dictionary itself etc, but further structure levels are not supported by DB structure.
    • document size has hardwired limit 16MB (in 2010 increased from 4 to 16MB and devs do not want to change it). CSPAD 2Mpix*8byte(double) = 16MB, but we may expect larger detectors like Jungfrau, Epix, Andor, etc.
    • Larger data size is suggested to save using GridFS; split data for chanks and save chunks in the same DB in different collections.
    • JSON (text) object in MongoDB is presented in unicode...(UTF-8).  Data should be converted to unicode force and back in saving retrieving.
• schema-less DB looks interesting to certain extents, but in order to find something in DB there should be a schema...
• GridFS works fine with document size>16GB.

References

• https://docs.mongodb.com/manual/tutorial/install-mongodb-on-linux/http://api.mongodb.com/python/current/tutorial.html
• tutorial
• recover-data-following-unexpected-shutdown
• authorization