Redundant Array of Independent Disks, or RAID, is a way of keeping content on several hard disks at the same time. A RAID could be software or hardware based on the drives which are used - physical or logical ones, still what’s common between them is that they all function as just a single unit where info is saved. The biggest advantage of using a RAID is redundancy because the information on all drives will be the same at all times, so even in case one of the drives fails for some reason, the information will still be present on the rest of the drives. The overall performance will also improve because the reading and writing processes could be split between different drives, so a single one won't be overloaded. There are different types of RAIDs where the performance and fault tolerance could differ according to the exact setup - whether data is written on all the drives real-time or it's written on a single drive and then mirrored on another, what number of drives are used for the RAID, and so on.
RAID in Shared Hosting
The hard drives which we employ for storage with our ground-breaking cloud hosting platform are not the classic HDDs, but quick solid-state drives (SSD). They work in RAID-Z - a special setup developed for the ZFS file system that we work with. All of the content that you upload to your shared hosting account will be kept on multiple hard disks and at least 1 will be employed as a parity disk. This is a special drive where a further bit is included to any content copied on it. In case a disk in the RAID fails, it'll be changed without service disturbances and the data will be rebuilt on the new drive by recalculating its bits thanks to the data on the parity disk plus that on the other disks. This is done so as to guarantee the integrity of the information and together with the real-time checksum validation that the ZFS file system runs on all drives, you'll never have to concern yourself with losing any info no matter what.