How to Add RAID to Your Motherboard
One of the quickest ways to add functionality to any computer is by adding the appropriate expansion card. It's the same with RAID; just insert the controller card into the right expansion slot and you're ready to go whether the system supports it natively or not.
What is RAID and Why Do You Want It?
RAID stands for Redundant Array of Independent Disks and is a method for combining multiple SATA hard drives into a single logical unit for improved reliability, performance, or both. It commonly deploys in one of four configurations although there are others:
- RAID 0: Designed for pure performance, striping splits the data between two drives, so you can read and write in parallel. The advantage is that it's very fast; the tradeoff is that if either drive fails you effectively lose both.
- RAID 1: Designed for fault tolerance, mirroring writes the data to two drives at once. The big advantage here is that you can lose either drive without losing any data; the tradeoff is that you effectively lose half your total capacity to redundancy.
- RAID 5: Designed to balance performance and fault tolerance, this mode needs a minimum of three hard drives. It combines striping with parity, using part of each drive to store data to reconstruct the information on one other.
- RAID 10: This option mirrors two stripe sets; you still lose half your total capacity, but you also still gain double the transfer rate.
How Do You Choose a RAID Card?
Choosing the right card depends on what you're needing to do with it. Anyone planning serious server use needs a card with its own processor, chipset, and RAM to take over the overhead of managing parity calculations. However, these functions may not be necessary for basic RAID levels like RAID 0 and RAID 1. Two things you do need to pay attention to are the controller card's interfaces.
- Disk Interface: Most cards use a SATA interface, particularly the SATA III revision which offers 6 Gbps data rates. Some cards offer six SATA III ports but only support four drives through what's called First in Service or FIS. Your system can see all the drives but if you want to mount a fifth one you have to eject one of the first four.
- Computer Interface: Increased hard drive performance only counts if the controller card can get the data to the computer fast enough, which is where PCIe comes in. Most cards aim to fit in a PCI-Express x4 motherboard slot, but some only have an x2 interface. Always look for a native PCIe x4 card with full four lane support as a SATA III stripe set can easily saturate the two-lane PCI Express interface.