What's the impact on existing SRDF/S when new adaptive copy starts running

I was under the assumption that resuming an acp_disk synchronisation was a low priority SRDF "task" and that existing SRDF/S data streams were not impacted. I thought that the adaptive copy process would only use the "free" bandwidth so the "production bandwidth" would not be impacted.

Every day we're copying from 300 to 500 gigs of data using acp_disk and let it run for almost 2 hours. After this we switch to SRDF/A to get the data consistent and after a minute or 2 or 3 we do a suspend.

Everything worked just fine, but yesterday an SRDF/S customer complained that during this 2 hour period he experiences extreme slowness on his SAN attached disks. Considering the history of this customer and previous incidents, I'm pretty sure it has to do with our acp_disk sync which occurs every day.

What I would like to know is if we can change the priority of this acp_disk sync or at least explain to me why EMC says that adaptive copy is a low priority thing, while in fact other synchronous links ARE stil impacted.