WD Advanced Format: do I need to do something special?

[Yuri]

Following instructions here 
(http://ivoras.net/blog/tree/2011-01-01.freebsd-on-4k-sector-drives.html) I 
destroyed my previous ZFS pool with 512 byte sectors and did this:
gnop create -S 4096 /dev/ad4
zpool create mypool /dev/ad4.nop
zpol create mypool/mydir
zpool export mypool
gnop destroy /dev/ad4.nop
zpool import mypool

Now this command 'zdb -C data | grep ashift' shows ashift=12 (4096 byte 
sectors).

However, when I begin to copy a lot of files files into /mypool/mydir 
online radio player gets severely affected. Sound get interrupted all 
the time. Itrettuptions stop after 1-2 secs after I stop copying.
This didn't happen with sector size 512 bytes.

What is wrong?

Yuri