Redundant Arrays of Inexpensive Disks (RAID) is a technology for boosting storage performance and reducing the risk of data loss due to disk error. It works by storing data on multiple disk drives and is well supported by Fedora. It’s a good idea to configure RAID on any system used for serious work.
RAID can be managed by the kernel, by the kernel working with the motherboard BIOS, or by a separate computer on an add-in card. RAID managed by the BIOS is called dmraid; while supported by Fedora Core, it does not provide any significant benefits over RAID managed solely by the kernel on most systems, since all the work is still performed by the main CPU.
Using dmraid can thwart data-recovery efforts if the motherboard fails and another motherboard of the same model (or a model with a compatible BIOS dmraid implementation) is not available.
Add-in cards that contain their own CPU and battery-backed RAM can reduce the load of RAID processing on the main CPU. However, on a modern system, RAID processing takes at most 3 percent of the CPU time, so the expense of a separate, dedicated RAID processor is wasted on all but the highest-end servers. So-called RAID cards without a CPU simply provide additional disk controllers, which are useful because each disk in a RAID array should ideally have its own disk-controller channel.
There are six “levels” of RAID that are supported by the kernel in Fedora Core, as outlined in Table 6-3.
Table 6-3. RAID levels ...