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Introduction to Storage Area Networks – I
iSCSI & FCIP
Ashish Shah
Cisco Systems, Inc.
[email protected]
BITS Pilani Alumni Association (www.bitsaa.org)
Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
1
Agenda
iSCSI
–
–
–
–
–
What is iSCSI
Login and Session Establishment
Basic IO
Advanced Concepts
Initiators and Targets
FCIP
– What is FCIP
– FCIP Case Study
References
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Introduction to SAN – 1: iSCSI & FCIP
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iSCSI
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What is iSCSI
RFC3720 - Internet Small Computer Systems Interface
A 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
IP
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TCP
iSCSI
SCSI
Introduction to SAN – 1: iSCSI & FCIP
Data
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iSCSI Architectural Model
SCSI Applications (File Systems, Databases)
SCSI
Device-Type
Commands
SCSI
Generic
Commands
SCSI
Transport
Protocols
SCSI Block Commands
SCSI Stream
Commands
SCSI Commands, Data and Status
Parallel
SCSI Transport
FCP
SCSI over FC
iSCSI
SCSI over TCP/IP
TCP
Layer 3
Network
Transport
Layer 2
Network
Other SCSI Commands
IP
Parallel SCSI
Interfaces
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Fibre Channel
Introduction to SAN – 1: iSCSI & FCIP
Ethernet, PPP, HDLC…
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iSCSI Conceptual model
iSCSI Initiator Entity
Network Entity
– An object that can have multiple iSCSI
nodes
iSCSI node:
Iqn.com.cisco.init-1
iSCSI Node
Network Portal (10.1.1.2)
– Initiator or Target node
– Identified by an iSCSI Name
– iSCSI Target node can have multiple
LUs
IP Network
Network Portal
Network Portal
(IP 20.1.1.5)
iSCSI node:
Iqn.com.cisco.disk-1
Network Portal
(IP 20.1.1.20)
iSCSI node:
Iqn.com.cisco.disk-2
– Provides a mechanism to access the
iSCSI nodes
– Identified by a Network address (IP)
iSCSI Target Entity
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iSCSI Sessions
iSCSI 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
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Discovery Session Login
Initiator
TCP
iSCSI Initiator Login
(Discovery Session)
Target
Establish TCP Session
TCP port
3260
Command - Login
Session type: Discovery-Session
iSCSI
Driver
Optional Authentication Phase
Command - SendTargets
Response
Target list: com.cisco.Target-disk1
Com.cisco.Target-Disk2
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Target Session Login
Target
Initiator
TCP
Establish TCP Session
TCP port
3260
Command - Login
Session-Type: Normal-Session, Target: com.cisco.Target-disk1
iSCSI
Driver
Optional Authentication Phase
Operational Parameter Negotiation
After this completes we are in full feature mode
Command – SCSI commands
Normal SCSI commands…
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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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
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Introduction to SAN – 1: iSCSI & FCIP
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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
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iSCSI Packet Format
46–1500 Bytes
Destination Source
Address
Address
Preamble
8
6
Well-Known Ports:
21 FTP
25 SMTP
80 HTTP
3225 FCIP
3260 iSCSI
Type
6
IP
TCP
Data
FCS
2
iSCSI Targets
Will Listen on
This Port (by
Default)
4 Octet
Opcode
Opcode-Specific Fields
Length of Data (After 40-Byte Header)
Offset
Offset
Source
Source Port
Port
Destination Port
Sequence Number
Sequence
Number
Acknowledgement Number
Acknowledgment
Number
Reserved U A P R S F
Window
Reserved U A P R S F
Checksum
Urgent Pointer
Checksum
Options and Padding
Initiator-Task Tag
Opcode-Specific Fields
Data Field…
SCSI Encapsulated
TCP Header
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LUN or Opcode-Specific Fields
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iSCSI Read Sequence
Initiator
Target
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
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iSCSI Write Sequence
Initiator
SCSI Command : ITT: 100, CmdSN: 110, ExpStatSN 50
Target
R2T : ITT: 100, TTT: 10 R2TSN: 10
SCSI Data-Out: ITT 100, : 111, TTT: 10, DataSN: 1,
ExpStatSN: 1
SCSI Response: ITT 100, ExpCmdSN: 111, MaxCmdSN: 116,
StatSN: 50
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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
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Introduction to SAN – 1: iSCSI & FCIP
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iSCSI Initiators
Applications
File System
iSCSI Software
Driver
Block Device
Applications
File System
iSCSI Software
Driver and
Dedicated
Hardware
Block Device
SCSI Generic
SCSI Generic
iSCSI
iSCSI
TCP/IP Stack
TCP/IP Stack
NIC Driver
Adapter Driver
NIC Adapter
SCSI Adapter
NIC Driver
Adapter Driver
TOE Adapter SCSI Adapter
iSCSI
Windows & Linux iSCSI
initiators freely available
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iSCSI HBA: both iSCSI & TCP
offloaded to hardware
TOE: Only TCP Offloaded
Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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iSCSI Targets
Native iSCSI Targets just appearing in the market
iSCSI 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
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Introduction to SAN – 1: iSCSI & FCIP
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iSCSI Gateway on Cisco MDS
Real iSCSI Initiator
IP Addr 10.1.1.1
iqn.initiator.abc
iSCSI
IP
Network
Virtual iSCSI Target
IP Addr 10.1.1.2
iqn.target.abc
iSCSI
Virtual FC Initiator
pWWN 12:34…56
fcid 0x550001
FC
Fibre
Channel
Fabric
FC
FC Targets Presented
as iSCSI Targets
iqn.def.123
iqn.ghi.456
Real FC Target
pWWN 12:34…78
fcid 0x550002
iSCSI Initiators Presented
as FC Initiators
pWWN d
pWWN a
iSCSI
FC
IP
iSCSI
iqn.abc.123
iqn.jkl.555
iSCSI Storage View
BITS Pilani Alumni Association (www.bitsaa.org)
pWWN c
pWWN b
Fibre Channel SAN View
Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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FCIP
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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What is FCIP
RFC 3821 – Fibre Channel over TCP/IP
Method 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
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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FCIP…
Advanced features help throughput:
– Write Acceleration
• Spoofing Transfer Ready locally
– Tape Acceleration
• Spoofing Tape commands locally
– Compression
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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FCIP Case Study
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Introduction to SAN – 1: iSCSI & FCIP
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Cisco IT SAN Case Study
BEFORE FCIP: Host-Based Replication
Source: Cisco IT@Work Case Study: FCIP and
EMC SRDF/A. November 14, 2005
© 2005 Cisco Systems, Inc. All rights reserved.
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November 19, 2006
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Cisco IT SAN Case Study…
AFTER FCIP: Array-Based Replication
Source: Cisco IT@Work Case Study: FCIP and
EMC SRDF/A. November 14, 2005
© 2005 Cisco Systems, Inc. All rights reserved.
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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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
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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Q&A
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Introduction to SAN – 1: iSCSI & FCIP
November 19, 2006
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