RAID Systems — Hardware Architectures, Benefits, SelectionWhat RAID systems deliver, which architectures exist and when a dedicated controller makes sense Concept · Benefits · PC-based disk arrays · Platform-independent disk arrays · Hardware selection |
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What are RAID systems?
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A RAID system (originally redundant array of inexpensive disks, today redundant array of independent disks) organises multiple physical hard disks of a computer into a logical drive that delivers higher data security against single-disk failure and/or higher throughput than a single physical disk. While most computer techniques are designed to avoid redundancy (duplicate data), a RAID system deliberately creates redundant information — so that the array as a whole keeps working when individual components fail. |
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History and meaning of the term
The term was coined by Patterson, Gibson and Katz at the University of California, Berkeley, in their paper “A Case for Redundant Array of Inexpensive Disks (RAID)”. They investigated the option of running cheap hard disks in a unit as a logical drive to save the cost of one large (then expensive) disk. The increased failure risk of the array was to be addressed by storing redundant data; the individual arrangements were discussed as RAID levels.
Subsequent development pushed RAID into server applications that exploit the higher throughput and fault tolerance — the cost-saving aspect was abandoned. The ability to swap individual disks in a running system matches today's common reading: Redundant Array of Independent Disks.
A RAID system requires at least two hard disks. The disks operate jointly and form an array that is, in at least one respect, more capable than the individual disks.
Benefits of RAID systems at a glance
A RAID system can achieve several goals at once:
| Increased fault toleranceRedundant data storage allows continued operation even when individual disks fail — depending on the RAID level one or several disks may fail simultaneously. | Higher transfer ratesParallel access to multiple disks substantially increases throughput — especially with sequential workloads and sufficient concurrency. |
| Build large logical drivesSeveral physical disks appear to the OS as a single, much larger volume. | Hot-swap during runtimeReplacement of hard disks and capacity expansion during operation — without server shutdown, via drive caddies. |
| Cost reduction through scalingMultiple inexpensive disks instead of one expensive enterprise drive — with comparable or better total performance. | High system performanceCombines IO performance, capacity and redundancy in one tier — a baseline requirement for every productive server. |
The exact way the disks interact is specified by the RAID level. The most common are RAID 0, RAID 1, RAID 5 and RAID 10 — covered in detail in our article RAID Levels Explained. From a user or application perspective, a logical RAID drive is indistinguishable from a single hard disk.
PC-based disk arraysDEDICATED CONTROLLER SERVER-INTEGRATED These OS-dependent RAID systems require an external RAID controller installed in the existing server. Performance of the array is determined exclusively by the controller and the chosen hard disks. High-quality RAID controllers come with a powerful processor, at least 8 MB of on-board cache, real-time I/O analysis with adjustable cache parameters and Flash-ROM for easy firmware upgrades. Circuits on the board monitor temperature and voltage in the RAID enclosure, with software solutions reporting status to the system operator. For modern setups, SSD-SATA, SAS SSDs and NVMe PCIe disks are standard — modern tri-mode controllers support all three bus types in parallel. |
Platform-independent disk arraysEXTERNAL ARRAY PROFESSIONAL PERFORMANCE RAID systems with SCSI-to-SCSI connection (today increasingly SAS-to-SAS or Fibre Channel) are professional solutions for mid-sized network environments. The array attaches to the server's existing host bus adapter. The RAID controller inside the array handles all RAID functions — the system is configured and operated independently of the connected server's OS. Capabilities and feature sets vary by vendor and model. Modern systems easily exceed the early SCSI limit of 20 MB/s per channel — current SAS-12G arrays deliver multiple GB/s per path; NVMe-oF setups reach into the 10-GB range. Integrated controller circuits monitor and report temperature swings and disk failures. The data is communicated visually and logged to the system operator. Classic external form factors are Direct Attached Storage (DAS, single server), SAN (Storage Area Network, multiple servers via Fibre Channel or iSCSI) and NAS (Network-Attached Storage, file-level over Ethernet). Plus the dedicated class of storage servers for backup and archive duties. |
Do I still need a backup if I have a RAID?
Yes, absolutely. Although a RAID provides increased data security, that does not mean you can skip backing up to tape, and it does not make tape drives or tape libraries obsolete.
Because a RAID is not a backup. A RAID provides more data security than a single disk, but viruses, ransomware or operator errors can destroy data faster than you might like — and the RAID consequently mirrors them. An accidentally deleted file or compromised database is gone simultaneously across all RAID disks.
Therefore the right approach is a combination of RAID (for hardware-failure availability) and a multi-tier backup following the 3-2-1 rule. See our detailed series:
Which RAID levels exist?
The RAID-level catalogue ranges from simple striping without redundancy (RAID 0) through mirroring (RAID 1) and parity-based methods (RAID 5/6) up to combined arrangements (RAID 10, 50, 60). Each level solves a different trade-off between performance, usable capacity and fault tolerance. A complete explanation of all 14 RAID levels including a comparison table and concrete recommendations is in our separate article:
» RAID Levels Explained — from RAID 0 through 1, 5 and 6 to compound levels
Consulting on RAID systems and storage hardwarePlanning a new server with a RAID array, an external DAS/SAN expansion or upgrading an existing system? We help you select RAID controllers, hard disks and SSDs as well as drive caddies and enclosures — matched to your performance and availability requirements. Phone: +49 (0)7666 / 88499-0 · E-mail: sales@industry-electronics.com |
Related shop categories
| Controllers & RAIDRAID controllers Controllers (all) |
Hard disks & SSDHard disks SSD SATA · SSD SAS SSD PCIe · SSD M.2 |
Servers & storageServers · Rack-mount Storage server Storage NAS · Storage SAN |
| Enclosures & caddiesDrive caddies Drive enclosures |
Backup & tapeBackup solutions Band/Cartridge · Tape array |
Storage in generalStorage media Direct Attached Storage |
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Last updated: April 2026 · Lieske Elektronik · industry-electronics.com