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RAID 0 (also known as a stripe set or striped volume) splits ("stripes") data evenly across two or more disks, without parity information, redundancy, or fault tolerance. Since RAID 0 provides no fault tolerance or redundancy, the failure of one drive will cause the entire array to fail, due to data being striped across all disks.
Fault tolerance uses for representation, in place of , in certain Nested RAID levels (see below for fault tolerance calculation). m {\displaystyle m} is the number of disks in each mirror, rather than the total number of disks.
All implementations of RAID, redundant array of independent disks, except RAID 0, are examples of a fault-tolerant storage device that uses data redundancy. A lockstep fault-tolerant machine uses replicated elements operating in parallel. At any time, all the replications of each element should be in the same state.
RAID 5E, RAID 5EE, and RAID 6E (with the added E standing for Enhanced) generally refer to variants of RAID 5 or 6 with an integrated hot-spare drive, where the spare drive is an active part of the block rotation scheme. This spreads I/O across all drives, including the spare, thus reducing the load on each drive, increasing performance.
Those RAID systems made their way to the consumer market, for users wanting the fault-tolerance of RAID without investing in expensive SCSI drives. Fast consumer drives make it possible to build RAID systems at lower cost than with SCSI, but most ATA RAID controllers lack a dedicated buffer or high-performance XOR hardware for parity calculation.
A parity drive is a hard drive used in a RAID array to provide fault tolerance. For example, RAID 3 uses a parity drive to create a system that is both fault tolerant and, because of data striping, fast. [1] Basically, a single data bit is added to the end of a data block to ensure the number of bits in the message is either odd or even. [2]
In some RAID configurations, such as RAID 0, failure of a single member drive of the RAID array causes all stored data to be lost. In other RAID configurations, such as a RAID 5 that contains distributed parity and provides redundancy , if one member drive fails the data can be restored using the other drives in the array.
A fault-tolerant, parallel POSIX file system, with block (VMs) and object (S3) interfaces, and advanced enterprise features like multi-tenancy, strong authentication, encryption. Split-brain safe fault-tolerance is achieved through Paxos-based leader election and erasure coding. RozoFS: Rozo Systems GNU GPL v2: Linux