Netapp SnapMirror is an asynchronous method of mirroring files from one location to another. At my company we use it to replicate property images from one datacentre to another. I've always wondered what happens to the replica as SnapMirror is a block copy though obviously the destination may be different therefore it needs to do something 'smart' to correct the differences between the two filers.
The 'smart'ness is what is causing performance problems - so lets go through them.
Here is some of the output of a 'statit' on the SnapMirror replica. The filer is idle - its not doing any traffic and its not snapmirroring.
nas02*> statit -e