I used to have a ball of a time understanding about RAID levels were, back when I was supporting SUN Solaris systems back in 1999. It was something new to me and it was not your run-of-the-mill Intel PC setup. It was my first foray into the massive enterprise area and all the talk on redundancy and disk mirroring technology did make me lose a lot of brain matter. Nonetheless, once you understand something, the world will be clearer and here's a new RAID level to learn about - RAID 6.
On the Intel site, there's a great article called Understanding Intelligent RAID 6. They sum up the differences between RAID 5 and RAID 6 clearly. RAID 6 is conceptually very much like RAID 5 with one additional key feature: the ability to tolerate more than one drive failure without data access interruption or even worse—data loss. This is its chief advantage over RAID 5, and it's a big one.
Let's take the same scenario for a 14-disk RAID 6 array using a two-disk protection scheme. When a single disk suffers a total failure, the array can still tolerate either another complete failure or a bad block before entering the same state of vulnerability that a degraded RAID 5 array suffers from. This is possible because there are two redundant disks as opposed to just one. So with the loss of one disk, the array can proceed through a rebuild to a spare disk, and still be protected against data loss through the second redundant disk.
Promise Technology, Inc., the originator and leading supplier of SATA RAID data protection and storage solutions has a great RAID 6 controller called the SuperTrak EX8350 RAID controller and its a good choice if you are sourcing for one. I've seen their products everywhere, including Maxtor and Seagate.
The SuperTrak EX8350 RAID controller is a cost-effective high-performance, high-capacity solution for internal storage systems. With support for SATA 3Gb/s drives and Promise's proven RAID engine, the SuperTrak EX8350 RAID controller is designed to meet the needs of disk-to-disk backup, NAS storage, security and surveillance, video editing, and near-line storage.
SuperTrakR EX8350 Serial ATA RAID controller specifications:
* Eight SATA ports at 3.0Gb/s (300MB/sec)
* Storage capacity up to 16.0 terabytes (with eight 500GB drives x 4 controllers/ system)
* PCI-Express x 4 host bus interface
* Intel IOP333 XScale I/O processor (500 MHz)
* 128MB DDR ECC on-board controller cache
* Battery back-up module option
* Four controller support within a system
* Low profile form factor ideal for 1U/2U server
* Combine with the SuperSwap 4100 for an advanced internal storage system
* RAID 0,1,5,6,10, 50 and JBOD Supported
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