ZFS

Blandat

Re: Minimum number of Disks

If you have 2 disks, use mirroring (raidz would be no better)
If you have 3 disks, use 3-way mirror or raidz single parity (raidz2 would
be no better than a 3-way mirror)
If you have 4 disks, use 2 2-way mirrors or raidz single parity or raidz
double parity
bugzilla.samba.org bug 4715

They added the option to set "directory name cache size = 0" on a per share 
basis.  This has fixed my problems.

Tuning

vfs.zfs.prefetch_disable="1" 
vfs.zfs.arc_max="104857600" 
vm.kmem_size_max="1G" 
vfs.zfs.zil_disable="1" 
It has worked very well for me
(raidz, 1.2 TB pool, 4 GB RAM, ~60 file systems and twice as many
snapshots) after I added the following lines to loader.conf:

vm.kmem_size="1G" 
vfs.zfs.arc_min="64M" 
vfs.zfs.arc_max="512M" 
set max_vnodes on i386