Both software and hardware RAID support are available in ClearOS. If you plan on implementing hardware RAID, please read the section below regarding supported hardware. Before you decide to purchase an expensive hardware RAID controller card, consider the following passage from the experts at O'Reilly:
“Why the stigma? Well, there are a couple of reasons. For one, when software RAID first saw the light of day, computers were still slow and expensive (at least by today’s standards). Offloading a high-performance task like RAID I/O onto a CPU that was likely already heavily overused meant that performing fundamental tasks such as file operations required a tremendous amount of CPU overhead. (…) But today, even multiprocessor systems are both inexpensive and common.” - Derek Vadala - Managing RAID on Linux - O'Reilly
You can implement software RAID in ClearOS by selecting the Create Custom Layout option in the installation wizard. You can find tips and tricks about partitioning in the section Configuring Partitions and RAID.
Some hardware RAID controller cards are not true hardware controller cards. They are simple hard disk controllers with BIOS and drivers to do software RAID Support. If redundancy is your primary concern, then software RAID will serve you better than a quasi-hardware RAID support card. To quote (again) from the Managing RAID on Linux book from O'Reilly:
Supported hardware RAID cards:
Unsupported, but may work:
Unsupported and not recommended:
As a rule of thumb, if a hardware card is under USD $150, then it is probably not true hardware RAID and either not recommended or not supported.