Relocate NFS root FS for maintenance

[Greg <greg-sys@duchatelet.net>]

  Hi,

I don't know if it is the good place to ask for such a problem, if not 
please apologize.

I have a pseudo active/active NFSv4 configuration: 2 NFSv4 servers 
(1:1.1.2-6lenny1), exporting 3 filesystems. Each filesystem are 
connected to a SAN volume, via iscsi and multipath.

filer-01 :
/var/local                      
10.0.0.0/16(rw,fsid=0,crossmnt,insecure,async,no_subtree_check)
/var/local/large            
10.0.0.0/16(rw,insecure,async,no_subtree_check,no_root_squash,fsid=3)

filer-02 :
/var/local                      
10.0.0.0/16(rw,fsid=0,crossmnt,insecure,async,no_subtree_check)
/var/local/small           
10.0.0.0/16(rw,insecure,async,no_subtree_check,no_root_squash,fsid=1)
/var/local/medium      
10.0.0.0/16(rw,insecure,async,no_subtree_check,no_root_squash,fsid=2)

filer-01 share a volume on the first SAN, filer-02 share 2 volumes on 
the second SAN.

I have to do a firmware upgrade on the SANs, so I have to umount 
/var/local/* on the nfs servers. On way could be to relocate NFS root FS 
from /var/local to /var/maintenance with empty directories large, medium 
and small
But how to do that ? I try to change /etc/exports then exportfs -rvf, 
but got "Stale NFS file handle" on clients...

If not, is there a better way to do that, without to shutdown NFS servers ?

-- 
Greg