RAID, which is an acronym of Redundant Array of Independent Disks, is a software or hardware storage virtualization technology which enables a system to use many hard drives as one single logical unit. To put it differently, all drives are used as one and the info on all of them is identical. Such a setup has two huge advantages over using just a single drive to save data - the first is redundancy, so if one drive doesn't work, the info will be accessible through the others, and the second one is better performance since the input/output, or reading/writing operations will be distributed among a number of drives. There're different RAID types in accordance with how many drives are employed, whether 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, and many others. According to the exact setup, the error tolerance and the performance may differ.
RAID in Shared Website Hosting
The disk drives which we employ for storage with our outstanding cloud web hosting platform are not the standard HDDs, but fast NVMes. They operate in RAID-Z - a special setup designed for the ZFS file system that we employ. All of the content that you upload to your shared website hosting account will be saved 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 included to any content copied on it. In case a disk in the RAID stops working, it will be replaced without 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 remaining 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 need to worry about losing any info no matter what.