[CentOS] nfs slow?

Hi all, I'm migrating from Gentoo to CentOS... I'm experiencing a  
rather low performance in NFS r/w (as client).
NFS server is solaris (which exports zfs volumes via nfs). The very  
same exports were mounted with the same parameters (auto,nosuid,exec)  
on gentoo and centos server (bot x86_64)... It happens that centos is  
5-10 times slower either in read and write operations... Ok, I'll try  
to tune rsize and wsize, but does anybody have an hint on this low  
performance?

Thanks
d

Davide Cittaro
davide.cittaro at ifom-ieo-campus.it