MongoDB regular idle

We build mongodb on Windows Azure VM with 2GB memory. The biggest collection has about 10 million data. When we import data (loop insert) to this collection, MongoDB will be idle for a long time every hundreds records. I suspect there are some other heavy queries which cause idle, But I found it's regular and only happen when we open import function. 

I completely have no idea about what's happening in background and how to improve it.

Thanks for any help or response.

In inserting time, cpu high but disk low; in idle time, cpu low but disk write high

It seems MongoDB  write to memory temporally and flush to disk in batch. And the flush causing everything idle

Yes, that's exactly what's happening - you are being limited by disk
throughput capacity.

What version of MongoDB is this?  There've been some issues on Windows
(in Azur in particular) that have been mitigated somewhat in the
latest version (and should get better yet when Microsoft pushes a
hotfix for an issue on the Windows side).

Thanks Asya, the mongodb version is 2.6.3, I'm trying to download the latest version and upgrade windows patches. I will give you progress after testing.

Thanks very much, it seems to be solved in my testing after upgrade both mongodb and windows updates.