Storage and SAN glossary

Use this page when a lab introduces an unfamiliar term. Definitions describe the learning model; vendor implementations can add constraints. For authoritative protocol and platform detail, open the standards and vendor source shelf.

Storage foundations

Block storage: numbered fixed-size blocks presented to a host, which normally adds a filesystem or database layout.
File storage: named files and directories exported through a file protocol such as NFS or SMB.
Object storage: objects addressed by key and accessed through an API, with metadata stored alongside content.
LUN: a logical block-storage unit exposed by a target.
RAID: a method of combining devices for capacity, performance, and/or failure tolerance.
Erasure coding: protection that divides data into fragments and computes independent parity fragments.
Snapshot: a point-in-time logical view; it is not automatically an independent backup.
RPO / RTO: acceptable data-loss window / acceptable service-restoration time.
IOPS / throughput / latency: operations per second / bytes per second / time per operation.

Fibre Channel and SAN

Fabric: interconnected Fibre Channel switches operating as one routing domain.
WWPN: globally unique identifier for an FC port.
FCID: fabric-assigned address used for frame routing.
FLOGI: login that registers an endpoint with a fabric.
Name server: fabric directory mapping registered identities and attributes.
Zone: policy that controls which initiators and targets can discover one another.
Zoning: fabric-side visibility control; it does not replace array-side LUN masking.
ISL: inter-switch link carrying frames between switches.
RSCN: registered state-change notification sent after relevant fabric changes.
NPIV: multiple virtual FC identities sharing a physical port.

iSCSI and multipathing

Initiator / target: client that requests block I/O / service that presents block devices.
IQN: iSCSI Qualified Name used as an endpoint identity.
Portal: target IP address and TCP port used for discovery or login.
Session: authenticated iSCSI relationship between initiator and target.
Multipathing: host aggregation of redundant routes to the same logical device.
ALUA: protocol by which a target reports optimized and non-optimized paths.

AI data systems

Embedding: numeric vector representing content for similarity search.
RAG: retrieval-augmented generation, where external context is retrieved before generation.
KV cache: attention key/value state retained for active model tokens.
Checkpoint: persisted model or training state used to resume or deploy work.

Next step

Follow the Zero-to-SAN learning program or use the daily health-check runbook.