RAID, or Redundant Array of Independent Disks, is a technology of storing data on a number hard drives that work together as one logical unit. The drives can be physical or logical i.e. in the latter case a single drive is split into individual ones using virtualization software. In either case, the same info is kept on all of the drives and the basic benefit of employing this type of a setup is that in the event that a drive stops working, the data will still be available on the remaining ones. Having a RAID also boosts the performance since the input and output operations will be spread among a couple of drives. There are several types of RAID depending on how many drives are used, whether writing is performed on all drives in real time or just on one, and how the info is synced between the drives - whether it's written in blocks on one drive after another or it is mirrored from one on the others. All these factors suggest that the error tolerance as well as the performance between the various RAID types can vary.
RAID in Shared Hosting
The hard drives that we use for storage with our top-notch cloud web hosting platform are not the classic HDDs, but high-speed solid-state drives (SSD). They work in RAID-Z - a special setup developed for the ZFS file system which we work with. All the content that you upload to the shared hosting account will be held on multiple hard disks and at least one shall be used as a parity disk. This is a specific drive where an additional bit is added to any content copied on it. In the event that a disk in the RAID stops functioning, it will be changed with no service disruptions and the info will be rebuilt on the new drive by recalculating its bits using the data on the parity disk along with that on the other disks. This is done to ensure the integrity of the data and along with the real-time checksum validation that the ZFS file system performs on all drives, you won't ever have to concern yourself with losing any data no matter what.