2010 marks the 20th anniversary of the RAID (Redundant Array of Independent Disks) revolution that changed the data storage industry. RAID fits the bill as a truly revolutionary technology. For us less “computer savvy” types, the RAID technology allowed computer users to achieve high levels of storage reliability from low-cost and less reliable PC-class disk-drive components, via the technique of arranging the devices into arrays for redundancy.
Over the years, there have not been many radical departures of the fundamental concept of RAID, although the original configurations have mushroomed beyond the traditional RAID 0, 1, 5, into RAID 1E( mirroring) RAID 5, 6 (dual-parity RAID) and hybrid configurations such as RAID 10, 50, and 60. In the context of the popular Serial ATA (SATA) disk drives, RAID 6 has emerged as an important configuration. Virtually all RAID controller vendors have implemented RAID 6.
RAID 6 is also known as striped set with dual distributed parity. It provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high availability systems. This becomes increasingly important because large-capacity drives lengthen the time needed to recover from the failure of a single drive. Single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt: the larger the drive, the longer the rebuild will take. Dual parity gives time to rebuild the array without the data being at risk if a (single) additional drive fails before the rebuild is complete.
Battery backup is critical in data storage. Can you imagine the data that could be lost in a power failure? In case of a power loss, reliable battery power is required for RAID controllers to perform operations such as write-back cache, array expansion, logical drive extension, stripe size migration, and RAID migration. Some RAID cards vendors offer 72 hours of battery protection.
Taylor Ortiz, a storage industry analyst states that “the technology train keeps rolling.” The train he was talking about is the PCI Express (Peripheral Component Interconnect Express) or PCIe for short. Introduced by Intel in 2004, PCIe is a Solid State Drive (SSD). The 21st Century PCIe cards are used in consumer, server, and industrial applications, as a motherboard-level interconnect (to link motherboard-mounted peripherals) and as an expansion card interface for add-in boards for video, graphics, data storage, and WiFi applications. PCIe cards utilize lithium ion batteries for power backup as batteries are required to enable write-back caching. Since space is a premium, only lithium ion battery packs are used. During normal operation, the battery will typically cycle itself approximately every 3 months. During a conditioning cycle, the battery is discharged and fully recharged to maintain battery optimum life.