RAID, which is short for Redundant Array of Independent Disks, is a software or hardware storage virtualization technology which makes it possible for a system to employ several hard drives as one single logical unit. Put simply, all of the drives are used as one and the information on all of them is the same. This kind of a setup has two major advantages over using just a single drive to keep data - the first is redundancy, so in case one drive doesn't work, the information will be accessible through the remaining ones, and the second one is improved performance as the input/output, or reading/writing operations will be spread among multiple drives. There're different RAID types depending on the number of drives are employed, if reading and writing are both handled from all of the drives simultaneously, whether data is written in blocks on one drive after another or is mirrored between drives in the same time, etc. According to the exact setup, the fault tolerance and the performance vary.
RAID in Website Hosting
The disk drives that we use for storage with our innovative cloud Internet hosting platform are not the traditional HDDs, but high-speed solid-state drives (SSD). They work in RAID-Z - a special setup designed for the ZFS file system that we use. All the content that you add to your website hosting account will be held on multiple hard disks and at least one of them will be used as a parity disk. This is a special drive where a further bit is included to any content copied on it. In the event that a disk in the RAID fails, it'll be replaced without any service interruptions and the info will be recovered on the new drive by recalculating its bits using the data on the parity disk plus that on the remaining disks. This is done to ensure the integrity of the information and together with the real-time checksum verification that the ZFS file system performs on all drives, you will never need to concern yourself with losing any data no matter what.