should we compare the old and new objects an update before writing?

what i'm thinking is that if we're writing the same object out - it may incur a dirty bit set on the page when it doesn't need to be.
which could lead to more disk activity.

we'll already have to read the page in - so its just the comparison that we add. and we only have to do it if they are exactly the same size. my guess is if the object changes - most of the time the size will change anyway.