If you're running Windows, you should be able to run the Array Configuration Utility (ACU). Look for it under the Programs\HP System Tools (or something like that); that's assuming it is installed.
(This is from memory so it may be a bit off)
Select the array controller on the left (if you only have one it should default to it)
Look at the logical drive (middle panel). Next to logical drive, it should tell you the size and RAID level, if not select "More Information" from the right.