RAID, or Redundant Array of Independent Disks, is a technology of storing data on several hard drives that work together as one logical unit. The drives could be physical or logical i.e. in the latter case one drive is divided into different ones using virtualization software. In any case, exactly the same info is saved on all drives and the key benefit of employing this type of a setup is that in case a drive breaks down, the data will still be available on the other ones. Having a RAID also improves the overall performance as the input and output operations will be spread among a few drives. There are several kinds of RAID based on how many hard disks are used, whether writing is performed on all of the drives in real time or just on one, and how the info is synchronized between the hard drives - whether it's recorded in blocks on one drive after another or all of it is mirrored from one on the others. These factors mean that the error tolerance as well as the performance between the different RAID types can vary.
RAID in Shared Hosting
The hard disks which we use for storage with our innovative cloud hosting platform are not the standard HDDs, but fast solid-state drives (SSD). They work in RAID-Z - a special setup developed for the ZFS file system which we employ. All the content that you upload to the shared hosting account will be stored on multiple hard drives and at least one of them shall be used as a parity disk. This is a special drive where an extra bit is added to any content copied on it. If a disk in the RAID stops working, it will be replaced without any service disturbances and the information will be rebuilt on the new drive by recalculating its bits thanks to the data on the parity disk plus that on the remaining disks. This is done to ensure the integrity of the info and along with the real-time checksum validation which the ZFS file system runs on all drives, you will never need to concern yourself with losing any information no matter what.