RAID, or Redundant Array of Independent Disks, is a technology for saving data on multiple hard disk drives which work together as a single logical unit. The drives can be physical or logical i.e. in the aforementioned case one single drive is divided into different ones through virtualization software. In either case, exactly the same info is stored on all drives and the main benefit of using this kind of a setup is that in the event that a drive fails, the data will still be available on the other ones. Using a RAID also enhances the overall performance since the input and output operations will be spread among a couple of drives. There are several types of RAID based on how many drives are used, whether writing is carried out on all the drives in real time or just on one, and how the data is synchronized between the hard drives - whether it's written in blocks on one drive after another or it is mirrored from one on the others. These factors imply that the fault tolerance as well as the performance between the different RAID types may differ.
RAID in Shared Hosting
The drives that we use for storage with our ground-breaking cloud hosting platform are not the classic HDDs, but extremely fast solid-state drives (SSD). They function in RAID-Z - a special setup created for the ZFS file system which we work with. Any content that you upload to your shared hosting
account will be kept on multiple disk drives and at least 1 will be employed as a parity disk. This is a special drive where a further bit is added to any content copied on it. In the event that a disk in the RAID stops functioning, it will be replaced without service disruptions and the information 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 in order to ensure the integrity of the data and together with the real-time checksum verification that the ZFS file system runs on all drives, you'll never need to concern yourself with losing any information no matter what.
RAID in Semi-dedicated Hosting
The data uploaded to any semi-dedicated hosting
account is kept on SSD drives that operate in RAID-Z. One of the drives in this kind of a configuration is used for parity - each time data is cloned on it, an additional bit is added. If a disk happens to be faulty, it will be removed from the RAID without interrupting the work of the sites because the data will load from the other drives, and when a new drive is added, the information which will be copied on it will be a mix between the data on the parity disk and data kept on the other hard disks in the RAID. That is done to ensure that the info which is being cloned is accurate, so once the new drive is rebuilt, it can be integrated into the RAID as a production one. This is an extra guarantee for the integrity of your information as the ZFS file system which runs on our cloud hosting platform compares a unique checksum of all copies of the files on the different drives to be able to avoid any chance of silent data corruption.