[root@centosgluster1 Tom_RDP_server]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      43104752   3317076  37562732   9% /
/dev/sda1               101086     20485     75382  22% /boot
tmpfs                 12305872         0  12305872   0% /dev/shm
localhost:/nfs       10107220480 -2566235075712 2576342296192   -  /mnt/nfs
[root@centosgluster1 Tom_RDP_server]# 

We can see that used space is -ve.

the setup has 4 servers -> distribute+nfs_xlator

This behavior is seen with just point-to-point connection too i.e simple client-server connection with out nfs_xlator too. The server is running on Solaris and client on linux.