Unfortunately on this forum, questions on performances are too often replied with:
- you have poor hardware, upgrade it
- you don't have 128GB of RAM, ZFS will not work properly
- you don't have an Intel NIC, it cannot work
- don't use RAIDZ1
- don't use 4 HDD with RAIDZ1
- samba is bad, slow, single threaded, don't use it, use ftp or nfs instead
- .....
It's always your fault if you don't have good performances... But this time it is not, it's just the default settings of samba which are broken.
This solved my problem completety:
http://forums.freenas.org/index.php?threads/browsing-directories-slow.5338/page-6#post-139295