I start with way of debugging. So can someone suggest how to debug
slow performance issue in NetApp filer. I mean what all I should check
before coming to any conclusion.

During slow performance I found deffered back-to-back-copy in
"sysstat" output and around 20% full stripe write in "statit"output.

May be it due to fragmentation in write block, fragmentation at file
level but how to conclude which is the problem and how to resolve.

As of now as a practice we run "wafl scan reallocate" on all volumes
and problem gets resolve for some time. we use traditional volume yet
and in our environment average file size is very less and also heavy
turnaround of files. For ex. 1TB volume has more that 30m files.

Please suggest how to handle the situation.