Membase "freezes" for seconds

Hello,

I have membase Version: 1.7.2r-20-g6604356
normally i get around 100 ops per second but every now and then membase starts to "freeze" for second or two and ops drop to 0 for second-2 and then spike to 200 due to alot of requests.
i have disk persistence set on my bucket, could it be due to that?

Thanks