[root@filer ~]# du -hs /tmp/test*
 98M    /tmp/test1
 98M    /tmp/test2
 98M    /tmp/test3
[root@filer ~]# zpool create test raidz /tmp/test1 /tmp/test2
[root@filer ~]# df -h | grep test
test                    61M      0B     61M     0%    /test
[root@filer ~]# dd if=/dev/urandom of=/test/test bs=512
dd: /test/test: No space left on device
123744+0 records in
123743+0 records out
63356416 bytes transferred in 295.913366 secs (214105 bytes/sec)
[root@filer ~]# df -h | grep test
test                    61M     61M      0B   100%    /test
[root@filer ~]# zpool add -f test /tmp/test3
[root@filer ~]# df -h | grep test
test                   154M     61M     93M    39%    /test
[root@filer ~]# dd if=/dev/urandom of=/test/test bs=512
dd: /test/test: No space left on device
313317+0 records in
313316+0 records out
160417792 bytes transferred in 280.602999 secs (571690 bytes/sec)
[root@filer ~]# df -h | grep test
test                   153M    153M      0B   100%    /test