Hi,
Other IOPs are anything that isn't a read or a write. The op count should be very low in FC/iSCSI environments, but can be significant in some NAS workloads since the storage presents the filesystem. So actions like "get file list in directory" or "get last modification date of a file" result in an other IOP that the storage controller will have to serve. Windows clients (especially older ones that run SMB 1 like win xp) are very chatty and issue a lot of other IOPs. Software build environments over NFS also typically have high other IOPs. Sometimes people also have software that walk the filesystem from their client (either on purpose, or part of some poorly written code) that generate a lot of other IOPs.
So to answer your question, there is no "normal" level. If the level is high it's because your clients are issuing those IOPs. For a point in time view of which volumes are receiving those requests use "stats show volume:*:other_ops".
For how it affects performance, other IOPs typically consume little disk IO (assuming there is enough system memory or flashcache/flashpool these are usually cached) but they do consume CPU to respond to.
Hope this helps!
Cheers,
Chris Madden
Storage Architect
NetApp EMEA