Introduction to SAN – 1: iSCSI & FCIPBITS Pilani Alumni Association ()1November 19, 2006...

BITS Pilani Alumni Association (www.bitsaa.org) 1November 19, 2006

Introduction to SAN – 1: iSCSI & FCIP

Introduction to Storage Area Networks – IiSCSI & FCIP

Ashish ShahCisco Systems, Inc.

[email protected]



Agenda

iSCSI– What is iSCSI– Login and Session Establishment– Basic IO– Advanced Concepts– Initiators and Targets

FCIP– What is FCIP– FCIP Case Study

References



iSCSI



What is iSCSI

RFC3720 - Internet Small Computer Systems InterfaceA SCSI transport protocol that operates on top of TCP– Encapsulates SCSI CDBs (Command Descriptor Blocks) and data into

TCP/IP byte-streams– Allows IP hosts to access IP based SCSI targets

Broad industry support– Server vendors now publishing own supported iSCSI drivers– Native iSCSI storage arrays now appearing

IPIP TCPTCP iSCSIiSCSI SCSISCSI DataData



iSCSI Architectural Model

SCSI Block Commands SCSI StreamCommands

Parallel SCSI Transport

SCSI Applications (File Systems, Databases)

Parallel SCSIInterfaces

SCSIDevice-TypeCommands

SCSIGeneric

Commands

SCSITransportProtocols

Layer 3 Network

Transport

Layer 2Network Fibre Channel Ethernet, PPP, HDLC…

Other SCSI Commands

IP

TCP

SCSI Commands, Data and Status

FCPSCSI over FC

iSCSISCSI over TCP/IP



iSCSI Conceptual modelNetwork Entity– An object that can have multiple iSCSI

nodes

iSCSI Node– Initiator or Target node– Identified by an iSCSI Name– iSCSI Target node can have multiple

LUs

Network Portal– Provides a mechanism to access the

iSCSI nodes – Identified by a Network address (IP)

Network Portal (10.1.1.2)

Network Portal (IP 20.1.1.5)

Network Portal (IP 20.1.1.20)

IP Network

iSCSI Initiator Entity

iSCSI Target Entity

iSCSI node: Iqn.com.cisco.init-1

iSCSI node: Iqn.com.cisco.disk-1

iSCSI node: Iqn.com.cisco.disk-2



iSCSI SessionsiSCSI has the concept of a session between an initiator and a target– Loosely equivalent to a SCSI I-T Nexus– It can have one or more TCP connections– Session establishment has three phases

• Security authentication, Operational negotiation and Full Feature

Discovery Sessions– Discover the targets in the network entity– Initiator executes “SendTargets” command after establishing the session

• This is the only command supported for a Discovery session

Target Sessions– Sessions to specific targets– Supports normal SCSI commands



Discovery Session Login

ResponseTarget list: com.cisco.Target-disk1

Com.cisco.Target-Disk2

Session type: Discovery-Session

TCP port 3260TCP port 3260

TargetInitiatoriSCSI Initiator Login (Discovery Session)

Establish TCP SessionTCPTCP

iSCSI DriveriSCSI Driver

Command - SendTargets

Command - Login

Optional Authentication Phase



Target Session Login

TCP port 3260TCP port 3260

TargetInitiator

TCPTCP

iSCSI DriveriSCSI Driver

Establish TCP Session

Command - LoginSession-Type: Normal-Session, Target: com.cisco.Target-disk1

Optional Authentication Phase

Operational Parameter Negotiation

After this completes we are in full feature mode

Command – SCSI commandsNormal SCSI commands…



Common iSCSI Identifiers

PGT: Portal Group Tag– Tag identifying a set of Network Portals that can support sessions with

multiple connections spanned across these portals

ISID: Initiator Session Identifier– Specified by the initiator during login

SSID: Session Identifier– Composed of the {ISID, Target PGT}

TSIH: Target Session Identifying Handle– A Target assigned tag to identify sessions on its end

ITT: Initiator Task Tag– Identifies an iSCSI Task



iSCSI Naming

iSCSI name can be either :– IQN (iSCSI Qualified Name)

• iqn => iqn.yyyy-mm.reverse-FQDN-[:|.]-and-qualifier-string• For example, iqn.1921-02.com.cisco.cluster1.mbr2

– EUI-64 name (Extended Unique Identifier)• eui.EUI-64 • For example, eui.02004567A425678D



iSCSI Packet Format

DestinationAddress

SourceAddress Type IP

46–1500 Bytes

8 6 6 2

FCS

4 Octet

Preamble

TCP Header SCSI Encapsulated

Source Port

Sequence Number

Acknowledgment Number

Checksum

Offset Reserved U A P R S F

iSCSI Targets Will Listen on This Port (by

Default)

Source Port Destination PortSequence Number

Acknowledgement NumberOffset Reserved U A P R S F Window

Checksum Urgent PointerOptions and Padding

Opcode Opcode-Specific Fields

Length of Data (After 40-Byte Header)

LUN or Opcode-Specific Fields

Initiator-Task Tag

Opcode-Specific Fields

Data Field…

TCP Data

3260 iSCSI

Well-Known Ports:21 FTP25 SMTP80 HTTP3225 FCIP



iSCSI Read SequenceTargetInitiator

SCSI Command : ITT: 100, CmdSN: 110, ExpStatSN 50

SCSI Data-In: ITT 100, ExpCmdSN: 111,

MaxCmdSN: 115, DataSN: 1

SCSI Response: ITT 100, ExpCmdSN: 111, MaxCmdSN: 116,

ExpDataSn: 3, StatSN: 50



iSCSI Write SequenceTargetInitiator

SCSI Command : ITT: 100, CmdSN: 110, ExpStatSN 50

SCSI Data-Out: ITT 100, : 111, TTT: 10, DataSN: 1,

ExpStatSN: 1

SCSI Response: ITT 100, ExpCmdSN: 111, MaxCmdSN: 116,

StatSN: 50

R2T : ITT: 100, TTT: 10 R2TSN: 10



More iSCSI Concepts

Error Recovery Levels (ERL 0/1/2)– Progressively higher level of error recovery capability

• 0 => Session failure recovery• 1 => Digest failure recovery• 2 => Connection recovery

iSCSI Header and Data Digests– Integrity protection only– Use of IPSec recommended for security

Task Management Functions– Derived from SCSI TMFs



iSCSI Initiators

NIC Adapter SCSI Adapter

iSCSI SoftwareDriver

NIC Driver Adapter Driver

TCP/IP Stack

iSCSI

SCSI Generic

Block Device

Applications

File System

SCSI Adapter

iSCSI SoftwareDriver and DedicatedHardware

Adapter Driver

iSCSI

TOE Adapter

NIC Driver

TCP/IP Stack

iSCSI

SCSI Generic

Block Device

File System

Applications

Windows & Linux iSCSI initiators freely available

iSCSI HBA: both iSCSI & TCP offloaded to hardwareTOE: Only TCP Offloaded



iSCSI Targets

Native iSCSI Targets just appearing in the marketiSCSI Gateway products have been on the market for a longer time– Exports backend FC targets through virtual iSCSI targets– Allows iSCSI initiators to access FC targets– Allows customers to introduce iSCSI initiators to existing FC SANs



iSCSI Gateway on Cisco MDS

iSCSI Initiators Presented as FC Initiators

FC Targets Presented as iSCSI Targets

pWWN a

Fibre Channel SAN View

pWWN bpWWN c

pWWN d

FC

iSCSI

Real iSCSI InitiatorIP Addr 10.1.1.1iqn.initiator.abc

IP Networ

k

Fibre Channel

FabricFC

FC

iSCSI

Virtual iSCSI TargetIP Addr 10.1.1.2iqn.target.abc

Real FC TargetpWWN 12:34…78

fcid 0x550002

iSCSI

iSCSI

iqn.abc.123

iqn.def.123 iqn.ghi.456

iqn.jkl.555

iSCSI Storage View

IP

Virtual FC InitiatorpWWN 12:34…56

fcid 0x550001



FCIP



What is FCIP

RFC 3821 – Fibre Channel over TCP/IPMethod to encapsulate FC traffic and send over an IP network– Encapsulating TCP connections are called FCIP Tunnels

Connects physically separate SANs through E/TE ports over an IP network– Forms a unified SAN in a single Fibre Channel fabric. – FC Fabric and all FC devices are unaware of the presence of the IP

Network

Motivation is to connect physically remote FC sites to allow remote disk access, tape backup and live mirroring



FCIP…

Advanced features help throughput:– Write Acceleration

• Spoofing Transfer Ready locally– Tape Acceleration

• Spoofing Tape commands locally– Compression



FCIP Case Study



iSCSI & FCIP References

IETF IP Storage (IPS) Chapter - http://www.ietf.org/html.charters/ips-charter.html– List of all relevant RFCs, mailing lists and working group details

Storage Networking Industry Association (SNIA)– www.snia.org



Q & A

Introduction to SAN – 1: iSCSI & FCIPBITS Pilani Alumni Association ()1November 19, 2006...

Documents

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