I can add my experience we had with an ERP system we use.
Windows front-end, Database back-end, file-system import/export/listing.
Write speed horrible. After tracing all traffic (using procmon.exe from sysinternals ) the application generated we concluded that the application was writing in small packages, one line at a time, with a file-open and a file-close after each line.
The strange thing was that on Windows shares (on another Workstation) this was not so much a problem, but running on Samba it slowed down to a crawl. Google: samba many small writes slow
http://ogre.ikratko.com/archives/347We demonstrated this the supplier, he changed the write routine so that it buffered and then flushed the write in one file-open/write/file-close. Problem solved.