Problem with md

[Sonia de Diego Atance]

Hi, I have got a problem with md. This is, when I do:
        mdadd /dev/md0 /dev/hdc /dev/hdd

tells me an error like:

/dev/hdc: No such device
/dev/hdd: No such device

But devices exist, because I can mount it.

I have RedHat 6.0 and kernel 2.2.5, also I am trying to update to 2.2.10

Thanks a lot

Sonia