This is actually a tip that should have gone into my previous post about MegaCLI but i feel it's more general than Linux and also it would have probably been lost in it so i think it's better if it got it's own post.
To address a disk in MegaCLI you usually enter the id of the enclosure followed by the id of the disk, all enclosed in brackets. However, internal disk don't have an enclosure and 0 will refer to the first external one so that won't work neither.
Instead you simply omit it. So to address the second internal drive simply use [:1] (remember index's start at 0).
This could be used with the following command to show info about a physical disk: megacli -pdinfo -physdrv[:1] -a0 (don't forget sudo if your system needs it).
Feel free to ask any questions or add comments regarding this post in the comments. I'll try and answer best i can, promise.