If your server is using Windows Operating system then using Device Manager you can identify if there's any RAID controllers installed.
On a Windows 2008 Server
Go to :-
My Computer
>> Properties
>> Click Device Manager, you will see a Storage Controllers option below the Processors option
>>Click on the + sign and you can check whether Raid is Present or not .
If you have a Linux Server then :-
To check if server have Hardware RAID, you can check using BIOS or any menu at the time of boot and to confirm if server is based on software RAID then you can use /proc/mdstat command.
Hope this helps you