iSCSI (Internet SCSI)

1
iSCSI (Internet SCSI)

• Storage Networking Industry Association IP
  Storage Forum
• White Paper

2
Outline

• Introduction
• SCSI
• iSCSI
• Network architecture
• Protocol model
• Address and naming convention

3
Introduction

• SCSI(Small Computer Systems Interface)
• The SCSI enables host computer systems to perform
  block data I/O operations to a variety of
  peripheral devices.
• distance limitation (up to 25m)
• New Technologies
• iFCP FCIP
• - high cost problem for FC
• - the lack of standardization
• iSCSI

4
Small Computer Systems Interface (SCSI)

• SCSI Architecture
• Based on a client/server model
• - The client(initiator) is a host system that
  issues requests to read or write data.
• - The server(target) is a resource such as a
  disk array that responds to client requests.
• A target has one or more logical units that
  process initiator commands.
• - LUN (Logical Unit Number)
• CDB(Command Descriptor Block)
• - issued by initiator
• - containing the commands that logical unit
  processes
• The central mission of iSCSI is to encapsulate
  and reliably deliver CDB transactions.

5
iSCSI Network Architecture

• Each host and storage resource supports a gigabit
  ethernet interface and iSCSI protocol stack.
• Internet Storage Name Service(iSNS)
• - name resolution service
• - facilitating device discovery for iSCSI
  initiators

6
iSCSI Protocol Model

• iSCSI uses TCP/IP for reliable data transmission
  over unreliable networks.
• The iSCSI layer includes encapsulated SCSI
  commands.
• An initiator may have multiple concurrent TCP
  connections.

7
iSCSI Address and Naming Conventions

• Each node has two network identities.
• iSCSI name
• - up to 255-bytes in length
• - unique human-readable identity
• iSCSI network address
• - combination of IP address and TCP port
  number
• - It is used for actual storage transactions
  between the initiator and
• the target.
• iSNS protocol is used for name resolution from
  iSCSI name to iSCSI address.
• - iSNS server the role of DNS

8
iSCSI write example

• iSCSI protocol data unit is used to send CDB
  commands, status and data.
• Ready to Transmit(R2T) PDU fulfills the role of
  upper layer SCSI flow control between target and
  initiator.

9
iSCSI Issues

• TCP/IP offload engine for optimum performance
• Ten Gigabit Ethernet can support higher
  populations of servers and storage devices.