mongorestore v3.0.1 is very slow compared to mongorestore in v2.6.9.

We have an exported dataset from mongo v2.4.2 about 17GB of data.

When we import this data into mongodb v.2.6.9 using mongorestore the process takes about 15 minutes.

When we import the same data into mongodb v3.0.1 the restore process take upwards of 3 days.

This test is performed on the same machine changing versions of mongodb and tools.

Is there any further information which can I provide to help?