I cann't see Disks for ASM Disk Groups as I install oracle linux64bit 11GR2 RAC

 I cann't see Disks for ASM Disk Groups as I install  oracle linux64bit 11GR2 RAC.

I cann't serch disk when I use 'Change Discovery Path" option.

Why cann't I see Disks for ASM Disk?

<my rac linux server information>

[root@rac1 ~]# oracleasm -V
oracleasm version 2.1.3

[root@rac1 ~]# oracleasm listdisks
DISK1
DISK2
DISK3
DISK4
DISK5

[root@rac1 ~]# rpm -qa |grep asm
oracleasm-2.6.18-194.el5-2.0.5-1.el5
oracleasm-support-2.1.3-1.el5
oracleasm-2.6.18-194.el5debug-2.0.5-1.el5
[root@rac1 ~]# uname -a
Linux rac1.localdomain 2.6.18-194.el5 #1 SMP Mon Mar 29 22:10:29 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux

[root@rac1 ~]# ls -al /dev/sd*