Question

here’s my problem:

I have a MongoDB Replica Set which I will have to use on extremelly slow connections (mainly inner africa, etc), I was wondering if other people over here have gone through something similar to this?

if so, could you please tell me how much is the replication capability on such a line?

if not, can you give me estimates?

I’ll be testing it out soon, but I’d really prefer to be prepared, I do know it won’t be slower than MySQL on these…

Thanks for your replies.

Answer 1

The type of bandwidth you’ll need depends on the size of the object you’re inserting or the size of the updates you’re making to existing objects; and obviously how many operations you’re performing a second. So we need to know more about the structure of your objects to give an idea of performance.

See this blog post (and other’s from Kristina) for details on the inner workings of the oplog so that you understand what is actually being replicated. http://www.snailinaturtleneck.com/blog/2010/10/12/replication-internals/

What you’re going to battle with is unreliable connections. In my experience, MongoDB doesn’t handle unreliable connections well. I’ve run replication between the US and UK and have had numerous problems where replication dies and simply doesn’t start again without manual intervention.

If you have large databases, you need to consider what you’re going to do if you have to resync your secondaries from scratch as it may take too long to bring them back online if you’re on slow connections.