FreeBSD 8.0 + ZFS : erratic network performances

[chris.compagnon at free.fr]

Hello !

I have installed a fresh freeBSD 8.0 (with kernel building, etc.)  and
activated ZFS.
There are 3 SATA disks for 1 raidz1 pool (through Promise TX4 contoler card).
and 1 IDE disk for cache.
(I remove the cache disk for testing --> Persitant problem)

With 1 GB or RAM and default parameters :

During transfering data to the ZFS server (through samba or FTP),
the data are temporaly stored on cache disk, so transfered on pool.
when the data pass from cache to pool, all transfers halt :
12 seconds : transfer
2/3 second : halt
12 seconds : transfer.
...

How obtain continuous transfers ?

Thanks.

Chris.