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iSCSI Protocol Analysis and Tools

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Setup and play with iSCSI SANs. Learn basic iSCSI troubleshooting skills ... Windows and Unix executables available. Supports traces captured by other analyzers ... – PowerPoint PPT presentation

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Title: iSCSI Protocol Analysis and Tools


1
iSCSI Protocol Analysis and Tools
  • Neeraj Reddy Kuppam neeraj_at_netapp.com

2
What are our goals today?
  • Learn iSCSI Protocol
  • Setup and play with iSCSI SANs
  • Learn basic iSCSI troubleshooting skills
  • Have Fun while learning!!!!

3
Blocks protocols
  • What is the relationship between SCSI, FC and
    iSCSI?

4
SCSI-3 - A path is a path
  • SCSI-3 is a client-server I/O protocol
  • Targets Data Provider/Server
  • 1 or more data containers called Logical Units
    (LUNs)
  • Initiators Data Consumer/Client
  • Reads/writes data in units of blocks
  • SCSI-3 is transport-independent Underlying
    transport mechanism and physical layer is not
    specified

5
SCSI-3 is Transport independent
Target
Initiator
LUN 0
LUN 1
Transport Mechanism
6
SCSI-3 CDBs Responses
Target
Initiator

SCSI_CMD LUN3 CDB28 00 00 10

DATA_IN Length4KB Data01 02
Transport Mechanism
7
FCP-SCSI Transport for SCSI-3

Target
Initiator

FC Frame FCP-SCSI Subtype SCSI_CMD LUN3
CDB28 00 00
FC Frame FCP-SCSI Subtype DATA_IN Length4KB
Data01 02
FC Port
FC Port
FC Fabric
8
iSCSI SCSI-3 over TCP/IP
  • iSCSI is a transport protocol for conducting
    SCSI-3 over standard TCP/IP networks
  • Defines message formats and rules
  • Operates as an Upper-Level Protocol within the
    TCP/IP networking framework
  • Peer to NFS, CIFS, HTTP, ...
  • Everything is a message Protocol Data Unit (PDU)

9
iSCSI Transport for SCSI-3
Target
Initiator


IP hdr TCP hdr iSCSI PDU SCSI_CMD
LUN3 CDB28 00 00
IP hdr TCP hdr iSCSI PDU DATA_IN
Len4KB Data01 02
Ethernet
Ethernet
GbE
10 GbE
10/100 Mbps
IP Network
10
Why do we need the iSCSI Protocol?
  • Benefits of SANs...
  • Familiar block-level access
  • Dedicated appliance for storage management
  • Shared access to centrally managed storage
  • without drawbacks of FC
  • No expensive dedicated FC infrastructure
  • Standard well-understood IP network routers,
    switches, cables, etc.

11
Before we jump in to iSCSI concepts.
  • Lets learn a little bit about
  • iSCSI analyzers.

12
iSCSI Protocol Analyzers
  • Hardware Analyzers
  • Finisar www.finisar.com
  • I-Tech www.i-tech.com
  • Agilent www.agilent.com
  • Software Analyzers
  • Ethereal www.ethereal.com
  • Network Associates SnifferPro www.mcafee.com
  • My Favorite
  • Ethereal www.ethereal.com
  • Its Free !!

13
iSCSI Protocol Analyzers Ethereal
  • Ethereal
  • Open Source Network Analyzer
  • Under GPL
  • Windows and Unix executables available
  • Supports traces captured by other analyzers
  • To name a few
  • tcpdump (libpcap), NAI's Sniffer Pro, NetXray,
    Sun snoop and atmsnoop, Shomiti/Finisar Surveyor,
    AIX's iptrace, Microsoft's Network Monitor,
    Novell's LANalyzer, RADCOM's WAN/LAN Analyzer,
    HP-UX nettl, i4btrace from the ISDN4BSD project,
    Cisco Secure IDS iplog, the pppd log
    (pppdump-format), the AG Group's/WildPacket's
    EtherPeek/TokenPeek/AiroPeek.

14
iSCSI Protocol by Example
  • iSCSI Protocol concepts

15
iSCSI Concepts Sessions
  • iSCSI Session
  • communication path and state between initiator
    and target
  • iSCSI realization of a SCSI-3 I_T_NEXUS
  • consists of one or more TCP connections
  • PLUS state of in-progress commands

Host
Target
Disk class driver
I_T_Nexus
SCSI Layer
SCSI layer (Target)
iSCSI Session
iSCSI Initiator
iSCSI Target
CMD1
TCP connections
CMD2
16
iSCSI Concepts Nodename, Aliases
  • iSCSI Nodename
  • Worldwide-unique nodename, prescribed format
  • Examples
  • iqn.1992-08.com.netappsn.35780522
  • iqn.2001-01.com.vendorhostname
  • eui.123456789abcdef0
  • iSCSI Target Alias, Initiator Alias
  • For convenient identification
  • Free format
  • Examples
  • oracle-host
  • qa-storage

17
PDUs
  • Each iSCSI message (I-gtT or T-gtI) is called a
    Protocol Data Unit (PDU)
  • 48-byte Basic Header Segment (BHS),
  • Variable-length data segment
  • PDU format

Opcode
Params
Data Segment Length
BHS
0
Params (e.g. CDB for SCSI_CMD PDU)
48
Data Segment
Data
18
iSCSI Protocol Stack the complete picture
19
iSCSI PDU types
  • LOGIN, LOGOUT create/shutdown session
  • SCSI_CMD, R2T, DATA_IN, DATA_OUT, SCSI_RESP
    messages for SCSI-3 command phases
  • TASKMGMT_CMD, RESP for AbortTask, ResetLUN,
    etc.
  • NOP_IN, NOP_OUT ping
  • ASYNCMSG Target reports event (e.g. abrupt
    shutdown)

20
Example iSCSI Write
  • Initiator Target

SCSI_CMD 16K LUN SCSI
CDB WRITE_EXT, 32KB First 16KB of DATA
R2T 0 Offset
16KB Length 16KB
DATA_OUT 16K Offset
16KB Last 16KB of DATA
SCSI_RESP 0 Response
SCSI_GOOD
21
iSCSI Target Discovery
  • Types of Discovery
  • Static Discovery
  • SendTargets Discovery
  • Dynamic Discovery
  • Lets look at a SendTargets Discovery trace

22
iSCSI Target Authentication
  • CHAP
  • Challenge Handshake Authentication Protocol
  • All iSCSI targets and initiators MUST support
    CHAP.
  • Users are likely to make mistakes in CHAP
    configuration.
  • Lets troubleshoot some authentication problems
    using traces.

23
After Target Discovery
  • Normal Session
  • Scanning for LUs
  • Lets look at a Bus Rescan Trace

24
Resources
  • Use the iSCSI trace reading ability you picked up
    today to troubleshoot common problems.
  • NetApp iSCSI Products
  • http//www.netapp.com/products/storage-networking
    /ipsan/index.html

25
I need your feedback.
  • Tell me now(or)
  • Send me an email.

26
Storage Simplified
27
Whats a FAS270c?


Heads
Shelves
Storage Controller

FAS270c HA in a box FCP!
28
FAS270c
Head 1
Head 2
Console port
2XGbE Cu NICS
FC (Fib)
FC (Cu) Shelf Expansion Port
29
NetApp Unified Storage Architecture
SAN
NAS
Departmental
CorporateLAN
NAS(File)
NetApp Fabric Attached Storage
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