Hitachi 9900 manual Mplf, Mtbf, Mttr, Nas

Hitachi Data Systems

Metadata

Data about data as used by the CM-HSM and the Control Memory Subsystem of the Lightning 9900 V Series.

Mirrored Pair

Two disk units or logical units that contain the same data. The operating system software refers to them as one entity and “reads from either” and “writes to both” when RAID-1 is enabled.

Mirroring

A term to describe the process of writing data to two disk volumes, usually to ensure high availability in case one of the disks fails. Mirroring can be hardware or software based.

MPLF

The Lightning 9900™ V Series supports the Multiple Path Locking Facility (MPLF) for the IBM® highest performance transaction processing operating system – TPF. In either native TPF mode or under VM, MPLF provides extremely high performance record- level locking so that multiple hosts can read and write to the same file without interfering with each other. See also TPF.

MTBF

Mean Time Between Failure. A commonly used measure of system reliability, usually expressed in hours. Modern disk drives typically have an MTTR of 1 million hours or more.

MTTR

Mean Time To Repair. Includes the time taken to diagnose the failure, replace or repair faulty component(s), and restart the system so it is available to users. See MTBF.

NanoCopy™

NanoCopy is a feature of the Hitachi Freedom Storage™ Lightning 9900™ V Series product line that enables time-consistent snapshots to be taken without stopping applications to flush in-flight data to disk. Since there is no system impact in taking a NanoCopy snapshot, snapshots can be made more frequently for faster recovery in the event of a failure. See also Hitachi TrueCopy™, Hitachi ShadowImage™.

NAS

Network Attached Storage or NAS servers are a special class of server that allows files to be stored over networks using the UNIX ® of Microsoft® Windows® remote file system standards.

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