Архитектура модульной системы хранения данных Front-End SCSI Target

Архитектура модульной системы хранения данных Front-End, SCSI Target

Contents • Configurations • SCSI Model – – – Architecture Model Standards Family Standards Architecture Distributed Service Model Client-Server Model • SCSI Commands – – – Command Descriptor Block Primary Commands Block Commands Task Management Functions Persistent Reservations

Configurations. Single Controller

Configurations • Single Controller • Dual Controller (DC) Active-Passive* Active-Active • • Symmetric Active-Active Asymmetric Active-Active** *RAIDIX AAP - Asymmetric Active Passive **ALUA - Asymmetric Logical Unit Access

Configurations. Dual Controller

Configurations. Dual Controller Target port access states: • Active/optimized • Active/non-optimized • Standby • Unavailable • Offline (AA, AP) (AA, AP)

Configurations. Dual Controller. ALUA

SCSI Architecture Model • Client-server model. • SCSI-based protocols. • Small Computer System Interface (SCSI) is a set of standards for physically connecting and transferring data between computers and peripheral devices. • The set of SCSI standards specifies the interfaces, functions, and operations necessary to ensure interoperability between conforming SCSI implementations.

SCSI Standards Family

SCSI Standards Architecture

T 10 Technical Committee

SCSI Distributed Service Model

SCSI Client-Server Model

SCSI Client-Server Model

Command Descriptor Block

Command Descriptor Block

SCSI Primary Commands Mandatory commands: • INQUIRY – determines the configuration of a logical unit (device type, vendor’s name, model number). • REPORT LUNS – reports of the logical units that are accessible to the host. • TEST UNIT READY – checks a logical unit if it is ready.

SCSI Block Commands Mandatory commands: • READ CAPACITY – describes the capacity and medium format of the direct access block device. • READ • WRITE

Task Management Functions • • • ABORT TASK SET CLEAR TASK SET I_T NEXUS RESET LOGICAL UNIT RESET

SCSI Persistent Reservations • Reservations may be used to allow a device server to process commands from a selected set of I_T nexuses and reject commands from I_T nexuses outside the selected set. • The device server uniquely identifies I_T nexuses using protocol specific mechanisms. • SCSI commands: – PERSISTENT RESERVE IN – identify which I_T nexuses are registered. – PERSISTENT RESERVE OUT – register an I_T nexus.