Disk Array Controller - Front-end and Back-end Side

Front-end and Back-end Side

Disk array controller provides front-end interfaces and back-end interfaces.

• Back-end interface communicates with controlled disks. Hence protocol is usually ATA (a.k.a. PATA; incorrectly called IDE), SATA, SCSI, FC or SAS.
• Front-end interface communicates with a computer's host adapter (HBA, Host Bus Adapter) and uses:
  • one of ATA, SATA, SCSI, FC; these are popular protocols used by disks, so by using one of them a controller may transparently emulate a disk for a computer
  • somewhat less popular protocol dedicated for a specific solution: FICON/ESCON, iSCSI, HyperSCSI, ATA over Ethernet or InfiniBand

A single controller may use different protocols for back-end and for front-end communication. Many enterprise controllers use FC on front-end and SATA on back-end.