Hi,
Again, I don't think that this sort of blanket "dissing" of reallocation is helpful.
With very high or very low deduplication rates (would be nice for NetApp to actually setup some basic thresholds) reallocation will simply be moving contiguous blocks together that belong together.
If I had, for example, 50 VDI images deduplicated with a 90% savings (and I do in places) then reallocation is basically just moving the datablocks together... the pointers wouldn't matter for the most part.
If I have a "CIFS" volume with 10% deduplication and perhaps lots of pretty large files, then reallocation is probably going to help.
There is, admittedly, a large area where reallocation probably won't help a lot, but it would seem very plausible that for the low and high deduplication cases that reallocation should give the same performance increases as for the "un-"deduplicated volumes.
I, like many of us, would really welcome more research from NetApp on the when and where and why's for these two seemingly contradictory file system operations.