I had asked a similar question of a NetApp engineer when we first got our F720. We also have Solaris 8 here. This may shed some light.
Question how is the NetApp configured? Meaning empasis on reads, writes, large files (xxMB) or small files (xKb) out of the box?
NetApp utilizes caching in two ways NVRAM and regular cache, but not in the conventional ways. When writes are received they are written in NVRAM (this is battery backed up), the write is acknowledged and you are on to the next task. As far as tuning the Filer there are really just a couple of options that can be turned off or on. The Filer is optimized to do one thing handle file I/O, it is not like a standard server or have the associated overhead. If you were looking at single file sizes over 5G there are some concerns, or smaller than 4K (we use 4K blocks so if a single file only took up 1K it would use a 4K block).