RAID Systems
System availability, contingency, security and data protection are the main reasons a RAID configuration is installed. The main feature of a RAID configuration is its redundant hard disk drive storage capacity. This feature allows the system to reconfigure and remain in service under disk storage failure conditions. High availability in RAID systems comes from the RAID controller's ability to switch to a redundant copy of data in the event of a single hard disk drive failure. The failure is not transparent to the users since performance is usually degraded whilst the reconfiguration process is in progress, which may take many minutes and in some cases a number of hours.
RAID systems achieve high capacity simply by using a multiple number of hard disk drives. With most RAID systems, the storage efficiency (the ratio of the RAID system capacity to the total capacity of all individual disks) is less than 100%. This is because most RAID systems keep redundant copies of the data and this data must be stored somewhere. Storage efficiency of a RAID system with redundancy IS usually 50% or higher
All RAID systems use the capabilities of multiple disks to improve performance. Performance is enhanced in different ways depending on the configuration. For example, since RAID 1 systems keep an exact redundant copy of data on another disk, they can read a file much faster since they read different parts of the file from each disk. RAID 0 arrays improve read and write performance by splitting files into pieces and storing the separate pieces on multiple disks.
It is important to note that not all RAID systems have all of these attributes. For example, RAID 0 does not provide any increased security or availability when compared to a single disk. RAID 0 systems are built for performance and capacity only.
For many years, RAID systems were used almost exclusively in high-end corporate data systems where cost of the system was not a concern. In recent years, the number of RAID users has grown dramatically. You may own a RAID system and use it everyday without even knowing it. For example, many high capacity external drives are nothing more than self-contained RAID 0 systems.
Here at Datlabs our RAID Guys specialize in the recovery of data stored on failed or inaccessible RAID systems. This recovery work involves rebuilding and restoring individual failed hard disks to a working condition, reconfiguring the data structures, extracting and repairing the data from the operational system. Read more...
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