SAN (Technologies, Protocols, Design)

  • A network of Storage devices
  • Seperates storage from the server
  • Benefits:
    • High I/O Ratings
    • Server Failover
    • Shared / Pooled storage
    • Lower TCO ( compared to direct storage)

SAN Components

  • Host Bus Adapter
    • Interfaces the device to the network
  • Datastorage
    • The drives within the san ( SAN speed + Uptime + Enterprise grade)
  • Storage Subsystems
    • RAID Settings ( Performance ~ Redundancy )

Protocols and Standards

  • SCSI
    • Older standard protocol, server / drive communication.
  • Parrallel Bus Standard
    • Half duplex
    • 16 device daisy chain
  • Fibre channel
    • 16 million device support
    • Speeds up to 4Gbps and now 128Gbps.
    • 10KM distance without extenders
    • Multiprotocol support
    • Fibrechannel is not Ethernet
    • Speedratings: 1,4,8,16,32,128Gbps

Fibre channel Communications

  • Very similar to TCP
    • Point-to-point session establishment ( 3-way handshake like)
    • Logical node connection point ( like TCP ports )
    • Fibre Channel Protocol ( FCP ) Supports flow control using ‘Buffer Credits‘ ( TCP Windows)
    • Multiple Sessions per device ( TCP Sockets )
  • Cisco MDS 9000 series switches design for this job.

Fibre channel Virtual SANs

  • A virtual SAN (VSAN) provides VLAN-like capabilities to a ‘SAN Island
  • Connections between switches ( ISL )
  • Cisco MDS 9000 uses Enchanced ISL
  • Inter-VSAN Routing ( IVR ) connects VSANS at Layer3. (Used with Fibre channel over IP (FCIP))
  • Parallel Universe; Fabric Shortest Path First ( FSPF ) Zoning.

REF:

https://supportforums.cisco.com/t5/data-center-documents/configuring-and-troubleshooting-mds-enhanced-zoning/ta-p/3118747

San Design

  • Similar to switch designs only on smaller scale
  • Cisco SAN MDS 9000
    • First Gen, Stackable Switches
    • Second Gen, Modular switches (less ISL , Redundancy)

Extending Fibre Channel

  • Within datacenter – Multimode / Single mode fiber
  • Metro – Dense wave Division Multiplex ( DWDM )
  • Anywhere – Fibre Channel over IP ( FCIP )
  • NOTE: ISCSI supports SAN extention over tcp/ip ( Not over Fibre Channel )
  • FCIP connects SAN to SAN, iSCSI connects Hosts to SAN
  • QoS absolutely needed for non-dedicated links.

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