There are two hard disks on my machine, but after installing the operating system, it uses only one hard disk to build RAID0.After installing MegaCLI, I used:MegaCli64 -pdlist -aALLto display the RAID configuration. I found one disk's Firmware state is online, but the other's is unconfigured.Does that mean I need to add the unconfigured disk to the RAID array? How do I add it? Before yesterday, I had no idea about RAID. Can someone advise me?
Use MegaCLI to add a new hard disk to existing RAID0 in Linux
hard disk;raid0
The problem is solved now.And Edouard Fazenda's method is right,but there is one step before adding a new virtual drive.In my case,when I used the command:storcli64 show all      or   MegaCli64 -CfgForeign -Scan -a0I found that the other hard disk's DG(DriveGroup) is foreign.I think that why I cann't use that hard disk to add a new virtual drive.So the first work is clearing it by the following commond:MegaCli64 -CfgForeign -Clear -a0After that,we can use the hard disk to add a new virtual drive by the following commond:MegaCli64 -CfgLdAdd r0[EnclosureID:SlotID] -a0     or  storcli64 /c0 add vd type=r0 drives=EnclosureID:SlotIDNow we can find sd[a|b|c...] directories in /etc,and we can use the hard disk normally.There is also some informations about this problem:[https://serverfault.com/questions/331807/megacli-is-killing-me-any-help-appreciated]In the end,I want to say thank you to @Warren Young and @Edouard Fazenda for giving so many clues to me.