Glossary L-N

L-N

Linear Tape Open (LTO)

A format for magnetic tape that competes with digital linear tape. LTO uses a linear multichannel bidirectional format but adds an enhanced timing-based servo (a device that automates a process of error correction for a mechanism), hardware data compression, and efficient error correction. Initially developed by a consortium of IBM, HP, and Seagate, it now has two different formats one for fast data access and another for greater storage capacity. The Accelis format uses 8mm tape on a two-reel cartridge that loads at the mid-point to provide fast data access, specifically for read-intensive applications. The other is the Ultrium format that uses a single reel of half-inch tape to maximize storage capacity, specifically for write- intensive applications, such as archival and backup functions. Ultrium-based products offer a >>100GB capacity, while some vendors are approaching the 1TB capacities .

LUN

A term used with addressing SCSI devices within a SCSI bus system. A logical unit number (LUN) is defined at the controller level to access, control, and manage the devices within the connected bus. LUNs provide a level of virtualization when communicating with the operating system, and subsequently the application, by shielding the application from the complexities of knowing physical addressing and access information for disk or tape I/O operations.

LUN management

The activities, functions, and capabilities that make up the manipulation, control, and assignments of LUNs within SCSI bus systems. These generally take the form of configuration parameters for controller initialization through microcode , but can assume higher levels of functionality, especially when managing multiple SCSI bus systems.

LUN masking

Part of LUN management where certain servers access specific SCSI devices within the shared SCSI bus environment, while other servers are blocked from accessing specific LUNs.

micro-kernel

A special type of operating system that can be optimized for a particular application. Both SAN and NAS devices use micro- kernels to provide base level operating system services to the SAN switch and NAS server, respectively.

MPP

A term used to describe a massive parallel-processing configuration. These configurations are made up of multiple processors (often numbering in the hundreds), sharing no system resources except a high-speed interconnect. They are currently used to address complex scientific, academic, or business analytical processing such as measuring earthquakes, nuclear explosions, and very high-end data warehouse applications, by breaking the application tasks into activities that can be processed in parallel. The processing nodes within MPP systems often have their own storage arrays; however, in some cases, some nodes have a common I/O configuration.

N_Port

The FC port that is designated for participating nodes, such as servers and storage arrays. These ports are configured through a Host Bus Adapter (HBA) and used to connect to the FC switch F_Ports.

NVRAM

A type of shared memory that is used by multiple system processors. Non-volatile random access memory is a portion of memory that ensures data integrity with the data that is written to the disk as multiple processor I/O operations take place across the same data.