This presentation include introduction to the SCSI cable followed by iSCSI protocol details.
Text of Detailed iSCSI presentation
1. Internet Small Computer System Interface iSCSI Sheel Sindhu Manohar IWC2013011 firstname.lastname@example.org
2. What is this?
3. PATA Cable
4. What is this?
5. SATA Cable
6. What is this?
7. SCSI Cable
8. SCSI Small Computer System Interface (SCSI) technology for I/O buses in Unix and PC servers. SCSI protocol defines how the devices communicate with each other via the SCSI bus. It specifies how the devices reserve the SCSI bus and in which format data is transferred. The SCSI protocol introduces SCSI IDs (aka. called target ID or just ID) and Logical Unit Numbers (LUNs) for the addressing of devices. The server can be equipped with many SCSI controllers. The operating system must note three things for the differentiation of devices controller ID, SCSI ID and LUN.
9. SCSI (2) Devices (servers and storage devices) must reserve the SCSI bus (arbitrate) before they may send data through it. During the arbitration of the bus, the device that has the highest priority SCSI ID always wins. Lower priorities never being allowed to send data if higher priority bus is heavily loaded SCSI devices connected in the form of daisy chain.
10. The SCSI I/O Channel SCSI is the dominant protocol used to communicate between servers and storage devices in open system SCSI I/O channel is a half-duplex pipe for SCSI CDBs and data Parallel bus evolution Bus width: 8, 16 bits Bus speed: 580 Mhz Throughput: 5320 MBps Devices/bus: 216 devices Cable length: 1.5m25m A network approach can scale the I/O channel in many areas (length, devices, speed) Applications Raw File System Block Device SCSI Generic TCP/IP Stack NIC Driver Ethernet NIC Ethernet SCSI CDB: SCSI Command Descriptor Block Used to Relay SCSI Commands, Parameters, and Status between SCSI Initiators and SCSI Targets; Typically 6, 10, or 12 Byte Block Adapter Driver Half-Duplex SCSI I/O Channel SCSI SCSI Adapter SCSI Initiator SCSI Target
11. SCSI and Storage Network SCSI suitable for the deployment of storage networks upto limited degree SCSI daisy chain can only connect a very few devices with each other. Although it is theoretically possible to connect several servers to a SCSI bus, this does not work very well in practice. The maximum lengths of SCSI buses greatly limit the construction of storage networks. Large disk subsystems have over 30 connection ports for SCSI cables Extend the length of the SCSI buses with so-called link extenders, the use of a large number of link extenders is unwieldy. SCSI having advantage that transition of SCSI cables to storage networks remains hidden from applications and higher layers
12. Different type of SCSI Interfaces
13. IP Based Storage IP storage is an approach to build storage networks upon TCP, IP and Ethernet. Three protocols are available for transmitting storage data traffic over TCP/IP: - iSCSI, - Internet FCP (iFCP) - Fibre Channel over IP (FCIP) The basic idea behind iSCSI is to transmit the SCSI protocol over TCP/IP iSCSI thus takes a similar approach to Fibre Channel SAN, the difference being that in iSCSI a TCP/IP/Ethernet connection replaces the SCSI cable
14. What is iSCSI? A SCSI transport protocol that operates over TCP/IP Encapsulates SCSI CDBs (operational commands: e.g. read or write) and data into TCP/IP byte streams Allows IP hosts to access IP-based SCSI targets (either natively or via iSCSI to FC Gateways) Standards status RFC 3720 on iSCSI Collection of RFCs describing iSCSI RFC 3347iSCSI Requirements RFC 3721iSCSI Naming and Discover RFC 3723iSCSI Security
15. iSCSI ISCSI refers to Internet Small Computer System Interface Enable location-independent data storage and retrieval. The protocol allows clients (called initiators) to send SCSI commands (CDBs) to SCSI storage devices (targets) on remote servers. It is a storage area network (SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts the illusion of locally attached disks. Unlike traditional Fibre Channel, which requires special-purpose cabling, iSCSI can be run over long distances using existing network infrastructure.
16. Concept iSCSI is often seen as a low-cost alternative to Fibre Channel, which requires dedicated infrastructure except in its FCoE (Fibre Channel over Ethernet) form. iSCSI is a mapping of SCSI-3 to TCP, as a SCSI transport. It behaves as a Serial SCSI transporter transferring SCSI packets (commands, data, status and control messages ) over a TCP stream. The idea is extremely simple, use existing building blocks ( SCSI, TCP ) to implement another service.
17. iSCSI Layers SCSI iSCSI Upper Functional Layers (e.g. SSL) TCP Lower Functional Layers (e.g. IPSec) IP LINK
18. IP Storage Networking IP storage networking provides solution to carry storage traffic within IP Uses TCP: a reliable transport for delivery Applicable to local data center and long-haul applications Two primary protocols: iSCSIInternet-SCSIused to transport SCSI CDBs and data within TCP/IP connections IP TCP iSCSI SCSI Data FCIPFibre-Channel-over-IPused to transport Fibre Channel frames within TCP/IP connectionsany FC framenot just SCSI IP TCP FCIP FC SCSI Data
19. Objective of iSCSI SAN iSCSI SANs often have one of two objectives: Storage consolidation Organizations move disparate storage resources from servers around their network to central locations, often in data centers; this allows for more efficiency in the allocation of storage. Disaster recovery Organizations mirror storage resources from one data center to a remote data center, which can serve as a hot standby in the event of a prolonged outage. In particular, iSCSI SANs allow entire disk arrays to be migrated across a WAN with minimal configuration changes.
20. For Storage Consolidation iS CS I IP access to open systems iSCSI and Fibre Channel storage iSCSI driver is loaded onto hosts on Ethernet network Able to consolidate servers via iSCSI onto existing storage arrays iSC SI Storage assigned on a LUN-byLUN basis at iSCSI router Logical Unit Number (LUN): A Field within SCSI Containing up to 64 Bits that Identifies the Logically Addressable Unit within a Target SCSI Device iS CS I iSCSI iSCSI Array (Target) Able to build Ethernet-based SANs using iSCSI arrays iSCSI-Enabled Hosts (Initiators) IP Network iSCSI Gateway FC Fabric Storage Pool (Target) FC HBAAttached Host (Initiator)
21. iSCSI Topologies Point-to-point direct connections Dedicated storage LAN, consisting of one or more LAN segments Shared LAN, carrying a mix of traditional LAN traffic plus storage traffic LAN-to-WAN extension using IP routers or carrier-provided "IP Datatone" Private networks and the public Internet