My initial concern was the overhead of block copying while the FlashCopy
logical drive is active, which for us is all day. This is made worse by
starting up an instance on that logical drive because now not only are
there block copies for initial writes to the primary, but also for
initial writes of blocks on the secondary. Plus, our secondary is on
the same server as the primary, so the penalty for nasty ad-hoc queries
on the secondary is almost the same as if it were run on the primary.
For us, this was not a problem after lots of testing showed that even
with the overhead, our new hardware was still muuuuuuuch faster than our
old system. :) I have not heard of a single performance problem
related to this in over two years of using it.
