Redundant Array of Independent Disks, or RAID, is a way of keeping content on a number of hard disks concurrently. A RAID could be software or hardware based on the hard drives that are used - physical or logical ones, however what’s common between them is that they all perform as one single unit where information is saved. The top advantage of employing a RAID is redundancy because the data on all of the drives is the same all of the time, so even in the event that one of the drives fails for some reason, the info will still be present on the rest of the drives. The general performance is also better since the reading and writing processes can be split between a number of drives, so a single one won't be overloaded. There're different sorts of RAIDs where the capabilities and fault tolerance may differ according to the exact setup - whether info is written on all of the drives in real time or it is written on a single drive and afterwards mirrored on another, what amount of drives are used for the RAID, and many others.
RAID in Hosting
The hard drives that we employ for storage with our outstanding cloud web hosting platform are not the standard HDDs, but extremely fast solid-state drives (SSD). They work in RAID-Z - a special setup designed for the ZFS file system which we employ. All of the content that you upload to your hosting account will be saved on multiple hard disks and at least one of them will be employed as a parity disk. This is a specific drive where a further bit is added to any content copied on it. In case a disk in the RAID stops working, it will be replaced without service interruptions and the data will be rebuilt 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 have to be concerned about losing any data no matter what.