mount 2 drives to 1 directory?
 

How to do it? I can't see the content in the folder after mounting sdc to /oradata

[root@demo ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 14112620 4986640 8409084 38% /
/dev/sdb 10321208 4294992 5501928 44% /oradata
none 259196 0 259196 0% /dev/shm

[root@demo ~]# mount /dev/sdc /oradata/
[root@demo ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 14112620 4986640 8409084 38% /
/dev/sdb 10321208 55836 9741084 1% /oradata
none 259196 0 259196 0% /dev/shm
/dev/sdc 10321208 55836 9741084 1% /oradata

[root@demo ~]# cd /oradata/
[root@demo oradata]# ls
lost+found


[root@demo /]# umount /dev/sdc
[root@demo /]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 14112620 4986640 8409084 38% /
/dev/sdb 10321208 4294992 5501928 44% /oradata
none 259196 0 259196 0% /dev/shm

You can't (not trivially, anyway, and with limitations
for the few ways that can be done [e.g. unionfs]) ...
what are you trying to achieve?