Why the jobs are suspended when I add new nodes?

[yang song]

Hi, all
    When I add another 50 nodes into the current cluster(200 nodes) at the
same time, the jobs run very smoothly at first. However, after a while, all
the jobs are suspended and never continue.
    I have no idea but to remove the new nodes. And the jobs run smoothly
again. Now I have to add nodes one by one. I won't add second node until the
jobs run smoothly after adding first node.
    Have you ever encountered the same situation? Could you give me some
tips and notes?
    Thank you!
    Inifok