Glossary - NEC S1300 User Manual

Glossary

A
Arbitrated Loop Technology
A Fibre Channel topology that provides an (FC-AL) solution to communicating ports in a
loop.
Arbitration
The process of selecting one respondent from a collection of several candidates that request service
concurrently.
Asynchronous Operations
Operations that bear no relationship to each other in time but can overlap. The concept of
asynchronous I/O operations is central to independent access arrays in throughput-intensive
applications.
B
Broadcast
Sending a transmission to all N_Ports on a fabric.
C
Cache Flush
Refers to an operation where all un-written blocks in a Write-Back Cache are written to the
target disk. This operation is necessary before powering down the system.
Channel
A point-to-point link, the main task being transporting data from one point to another.
Cluster
A group of independent computer systems working together as a single system, using a
shared disk storage such as a disk expansion unit (DEU). In a two-node cluster, both servers
are "active," i.e. servicing client requests just like two network servers. If one of the servers
fails, the surviving server initiates a "failover" and the applications running on the failed
server can be moved to the surviving server, transparently to clients.
Consistency Check
Refers to a process where the integrity of redundant data is verified. For example, a
consistency check of a mirrored drive will make sure that the data on both drives of the
mirrored pair are exactly the same. For RAID level 3 and 5 redundancy, a consistency
check will involve reading all associated data blocks, computing parity, reading parity, and
verifying that the computed parity matches the read parity.
Glossary 1
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