RAID, or Redundant Array of Independent Disks, is a technology of storing data on a number hard disks that work together as a single logical unit. The drives can be physical or logical i.e. in the aforementioned case one single drive is split into independent ones via virtualization software. In any case, the same information is stored on all the drives and the main advantage of using such a setup is that in the event that a drive fails, the data shall still be available on the remaining ones. Using a RAID also improves the performance since the input and output operations will be spread among a number of drives. There are several kinds of RAID based on how many drives are used, whether writing is done on all the drives in real time or just on one, and how the info is synchronized between the drives - whether it is written in blocks on one drive after another or all of it is mirrored from one on the others. These factors imply that the error tolerance as well as the performance between the various RAID types can differ.
RAID in Shared Hosting
The advanced cloud web hosting platform where all shared hosting accounts are made uses quick SSD drives instead of the classic HDDs, and they operate in RAID-Z. With this configuration, several hard disks work together and at least one is a dedicated parity disk. In simple terms, when data is written on the remaining drives, it's duplicated on the parity one adding an extra bit. This is done for redundancy as even in case a drive fails or falls out of the RAID for some reason, the information can be rebuilt and verified thanks to the parity disk and the data stored on the other ones, so not a thing will be lost and there will be no service disturbances. This is an additional level of protection for your information together with the state-of-the-art ZFS file system which uses checksums to ensure that all the data on our servers is intact and is not silently corrupted.