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UNH InterOperability Lab

iSCSI Introduction. UNH InterOperability Lab. Contents. Definition of iSCSI iSCSI vs Fibre Channel iSCSI Session Types Key Negotiation Overview. Definition of iSCSI. iSCSI is a Storage Area Network (SAN) protocol that allows for SCSI command transmission over a TCP/IP network

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UNH InterOperability Lab

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  1. iSCSI Introduction UNH InterOperability Lab

  2. Contents Definition of iSCSI iSCSI vs Fibre Channel iSCSI Session Types Key Negotiation Overview

  3. Definition of iSCSI iSCSI is a Storage Area Network (SAN) protocol that allows for SCSI command transmission over a TCP/IP network iSCSI allows for the sharing of I/O devices over a long distance, especially storage devices Typically high speed disk arrays

  4. Definition of iSCSI Continued iSCSI maintains the SCSI notion of an Initiator and Target device iSCSI removes the traditional bus structure of SCSI and maps SCSI over a network

  5. Bus Architecture Network Architecture Bus vs Network Architecture

  6. Problems Mapping SCSI to a Network In order not to violate Bus model of SCSI, there can only ever be one (1) concurrent Session between an iSCSI Initiator and iSCSI Target Commonly called “The ISID Rule” Multiple Connections may exist within that Session, but all Connections must contain the same Initiator Session Identifier (ISID)

  7. iSCSI vs Fibre Channel Both protocols have advantages and disadvantages iSCSI is typically less expensive Fibre Channel is typically faster

  8. iSCSI iSCSI is traditionally less expensive than Fibre Channel to implement Can be done with only software iSCSI can run over preexisting copper infrastructure and use preexisting switches and routers iSCSI does not require specially trained network administrators to manage the network

  9. Fibre Channel In most cases, Fibre Channel will outperform iSCSI in data transfer speeds Fibre Channel requires a special fiber network to be created in order to be implemented Total Cost of Ownership (TCO) is much higher than iSCSI Special network, administrators, fiber maintenance, etc.

  10. Comparison Conclusion Fiber Channel is much faster than traditional iSCSI iSCSI Extensions for RDMA (iSER) aims to lessen this difference iSCSI can run over preexisting copper infrastructure iSCSI devices can be accessed over the Internet In almost all cases, iSCSI is less expensive to implement and maintain

  11. iSCSI Session Types iSCSI has two (2) Session types Discovery Normal Each Session has two (2) Phases Login Contains Security Negotiation and Operational Parameter Negotiation Full Feature Phase

  12. Discovery Session A Discovery Session is used to allow the iSCSI Initiator to find iSCSI Targets that it can connect to The Initiator must explicitly tell the Target that the Session to be created be a Discovery Session SessionType=Discovery

  13. Login within Discovery Allows the Initiator and Target to establish 'who' it is

  14. Full Feature Phase within Discovery Once the Login Phase has completed, the Session can transfer into Full Feature Phase (FFP) Within a Discovery Session, FFP allows the sending of Text Requests (Initiator) and Text Responses (Target) Used to let the Target inform the Initiator what devices it can access No other types of data units may be transmitted

  15. Discovery Session • Initiator transmits the SendTargets key to the Target • Target replies with a list of devices accessible to the Initiator and their addresses

  16. Discovery Session Once a Discovery Session has completed, the Session must be terminated If the Initiator then desires to perform data I/O, a Normal Session must be created

  17. Normal Session An iSCSI Initiator will explicitly tell the iSCSI Target that the Session to be created is a Normal Session A Normal Session is defined in RFC 3720 to be an unrestricted session Access to SCSI devices can only be achieved while in a Normal Session

  18. Login within Normal Session Allows the Initiator and Target to declare/negotiate data transmission rules and other connection settings Ex. Size of individual data units, number of simultaneous data transfers

  19. Once Full Feature Phase (FFP) within a Normal Session has been reached, data I/O can take place Full Feature Phase in Normal Session

  20. Key Negotiation Overview All iSCSI parameters are contained within key=value pairs Ex. “TargetAlias=UNH-IOL” Some keys are declared and others are negotiated Declared keys do not need a response from the receiver Negotiated keys must always receive a response from the receiver

  21. iSCSI Key Negotiation • Key negotiations can allow the enabling or disabling of features • Also allows for value negotiation or declaration • Ex. MaxBurstLength=512 More on Key Negotiation will be covered in the iSCSI Login Presentation

  22. Summary • iSCSI is a low cost, low maintenance alternative to Fibre Channel • iSCSI networks can use existing copper infrastructures • Unlike Fibre Channel, iSCSI networks can span the Internet • iSCSI Key Negotiation allows for enabling/disabling of features as well as value negotiations

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