Raid, San | Hitachi 9900 instruction

Glossary

RAID

Redundant Array of Independent Disks. RAID is used to increase the reliability of disk arrays by providing redundancy either through complete duplication of the data (RAID-1, i.e., mirroring) or through construction of parity data for each data stripe in the array (RAID-3, -4, -5). RAID-5, which distributes parity information across all disks in an array, is among the most popular means of providing parity RAID since it avoids the bottlenecks of a single parity disk. The Hitachi Freedom Storage™ Lightning 9900™ V Series algorithms enable performance from RAID-5 that is competitive with some vendors’ RAID-1.

RAID Controllers

RAID controllers provide a highly optimized scheme for securely managing RAID configurations on storage systems. Hitachi RAID controllers allow RAID arrays to be expanded online and support conversion of an array from one RAID level to another.

Recovery Time

The period from the disaster declaration to the recovery of the critical functions.

Remote Copy

Remote Copy refers generically to software or hardware utilities that provide the capability to copy data from one online volume to remote volumes without disruption. Synchronous techniques are used for short distances (typically less than 25 miles), and asynchronous techniques over LAN/WAN/MAN are used at any distance.

Remote Copy Links

This term refers to the links used between storage systems for the movement of data. Today these links are either direct-connect ESCON®, Fibre Channel, or network links (T3, ATM, etc). For direct-connect ESCON there is a limit of 43km (25 miles). For direct-connect Fibre Channel the limit is 10km. However, newer technologies, such as the Nortel™ OPTERA™ product, are allowing direct fibre connect over longer distances.

Risk Management

The discipline that ensures that an organization does not assume an unacceptable level of risk.

SAN

Storage area networks (SANs) connect storage systems to servers through Fibre Channel or Ethernet switches. Hitachi's implementation of SAN is known as Hitachi SAN™ and falls under the larger Hitachi Freedom Data Networks™ umbrella. Major benefits of SANs include outboard backup, sharing of resources, pooling, and reduced cost of storage management. SANs are high-speed subnetworks of shared storage devices. SAN architecture works in a way that makes all storage devices available to all servers on a LAN or WAN. Because stored data does not reside directly on any of a network's servers, server power is utilized for business applications, and network capacity is released to the end user. See also Fibre Channel.