MongoDB vs Mysql Storage space compare

Question

I am building a data ware house that is the range of 15+ TBs. While storage is cheap, but due to limited budget we have to squeeze as much data as possible in to that space while maintaining performance and flexibility since the data format changes quiet frequently.

I tried Infobright(community edition) as a SQL solution and it works wonderful in term of storage and performance, but the limitation on data/table alteration is making it almost a no go. and infobright's pricing on enterprise version is quiet steep.

After checking out MongoDB, it seems promising except one thing. I was in a chat with a 10gen guy, and he stated that they don't really give much of a thought in term of storage space since they flatten out the data to achieve the performance and flexibility, and in their opinion storage is too cheap nowadays to be bother with.

So any experienced mongo user out there can comment on its storage space vs mysql (as it is the standard for what we comparing against to right now). if it's larger or smaller, can you give rough ratio? I know it's very situation dependent on what sort of data you put in SQL and how you define the fields, indexing and such... but I am just trying to get a general idea.

Thanks for the help in advance!

Answer 1

MongoDB is not optimized for small disk space - as you've said, "disk is cheap".

From what I've seen and read, it's pretty difficult to estimate the required disk space due to:

• Padding of documents to allow in-place updates
• Attribute names are stored in each collection, so you might save quite a bit by using abbreviations
• No built in compression (at the moment)
• ...

IMHO the general approach is to build a prototype, insert data and see how much disk space your specific use case requires. The more realistic you can model your queries (inserts and updates) the better your result will be.

For more details see http://www.mongodb.org/display/DOCS/Excessive+Disk+Space as well.