[DC] Storage Networking & FibreChannel

LAN and SAN Separation

• Security  Ensures protection from hacking
• Bandwidth – SAN needs more bandwidth than LAN
• Flow Control – SAN is lossless and LAN is lossy
  • Ethernet Flow control ( LAN ):
    • Source transmits packets untill receiver buffer overflow, then sends a “Pause” frame
    • Lost packets are retransmitted
  • Fibre Channel ( SAN ):
    • Credit based mechanism – Receiver has control
    • Source does not send a frame until the receiver telsl the source it can receive a frame by sending “Ready” signal Back
• Performance – SAN provides more performance than LAN enviorments

LAN vs SAN flow control

• Flow control is how data is controlled in a network
• Ethernet Flow control ( LAN )
  • Source transmits packets until receiver buffers overflow, then sends a “Pause” frame
  • Lost packets are retransmitted
• Fibre Channel ( SAN )
  • Credit based mechanism – Receiver has control
  • Source does not send a frame until the receiver tells the source it can receive a frame by sending “Ready” signal back.
  • “Lossless Fabric”

FibreChannel

• San Topologies
  • Point-to-Point
    • Initiator (server) and Target (Storage) directly connected
  • Arbitraded Loop (FC-AL) (Legacy)
    • Logical ring topology, similar to token ring
    • Implies connection is required on the ring
  • Switched Fabric ( FC-SW ) ( Standard)
    • Logical equivalent to a switched ethernet LAN
    • Switches manage the fabric allowing any-to-any communication
    • Support more than 16 million device addresses
• FibreChannel Port types
  • N_port – Node Port
  • NL_port – Node Loop Port
  • F_port – Fabric Port
  • FL_port – Fabric Loop Port
  • E_port – Expansion Port ( ISL )
  • TE_port – Trunking Expansion Port
• FC Addressing is analogous to IP over Ethernet
  • IP addresses are logical and manually assigned
  • Ethernet MAC Addresses are physical and burned in
  • FC World Wide Names ( WWNs )  / MAC / Zoning
    
    • 8 byte address burned in by manufacturer
    • Word Wide Node Name
    • World Wide Port Name
  • FC Identifier ( FCID )  / IP / Routing
    
    • 3 byte logical address assigned by fabric
    • FCID is subdevided into three fields:
      • Domain ID
        • Each switch gets a domainID
      • Area ID
        • Group of ports on a switch have an Area ID
      • Port ID
        • End station connected to switch gets a Port ID
• FibreChannel Nameserver ( FCNS)
  • analogous to ARP cache
  • Used to resolve WWN ( pysical address ) to FCID ( logical address )
  • Like FSPF, FCNS requires no configuration
• FibreChannel Logins
  • Ethernet networks are connectionless
  • Fibre Channel networks are connection oriented
    • All end stations must first register with the control plane of the fabric before sending any traffic.
  • Fabric Registration has three parts
    • Fabric Login ( FLOGI)
    • Port Login ( PLOGI)
    • Process Login ( PLRI )
  • sh flogi database
  • sh fcns database
• VSANs
  • Logical seperation of SAN traffic
• Zoning
  • like an ACL in the IP world