page_title: Standard RAID levels
section_title: RAID 4
hierarchical_section_title: Standard RAID levels / RAID 4
context_page_description: In computer storage, the standard RAID levels comprise a basic set of RAID configurations that employ the techniques of striping, mirroring, or parity to create large reliable data stores from multiple general-purpose computer hard disk drives. The most common types are RAID 0, RAID 1 and its variants, RAID 5, and RAID 6. RAID levels and their associated data formats are standardized by the Storage Networking Industry Association in the Common RAID Disk Drive Format standard. The numerical values only serve as identifiers and do not signify performance, reliability, generation, or any other metric.
  While most RAID levels can provide good protection against and recovery from hardware defects or defective sectors/read errors, they do not provide any protection against data loss due to catastrophic failures or soft errors such as user error, software malfunction, or malware infection. For valuable data, RAID is only one building block of a larger data loss prevention and recovery scheme – it cannot replace a backup plan.
context_section_description: RAID 4 consists of block-level striping with a dedicated parity disk.  As a result of its layout, RAID 4 provides good performance of random reads, while the performance of random writes is low due to the need to write all parity data to a single disk.
  In diagram 1, a read request for block A1 would be serviced by disk 0. A simultaneous read request for block B1 would have to wait, but a read request for B2 could be serviced concurrently by disk 1.
caption: Diagram 1: A RAID 4 setup with dedicated parity disk with each color representing the group of blocks in the respective parity block (a stripe)