Friday, June 14, 2013

Fiber Channel Fabric Services - (Storage Series Part-3)

Principle Switch (PS) Election

# Election starts when E port between two or more switches comes up

# Assign Domain IDs automatically but can be assigned manually as well 

   with - ( fcdomain domain 0x51 vsan )

- Preferred > Switch asks principal switch if it can use static domain id, if PS 

   says "Yes" than fine, If "NO" it uses Domain ID given by PS

- Static > Same theory as above but if PS says NO, the switch gets isolated from the FC network

Election based on

- Lowest priority ( fcdomain priority 1 vsan 1)
- Lowest WWN ( sh wwn switch)

* sh fcdomain (vsan)
* sh fcdomain domain-list (vsan)

FC Domain Services Restart

- Graceful - fcdomain restart vsan 1

- Forced - fcdomain restart disruptive vsan 1 < Hidden command

Everytime we make changes into FC Services, the services must be restarted


# Note: One copy of FC services runs on per VSAN basis which means One

  domain id can be used for multiple VSANs but it doesn't affect the design. 
  It's more like using one OSPF router id for multiple ospf processes. But each 
  process populates a separate Datbase which is completely unrelated from each other.


Fabric Shortest Path First (FSPF)

- Used to build an SPT through the fabric

- Domain ID is the Node ID in the SPT calculation

- FSPF runs automatically on per VSAN basis

- FSPF perameters can be manually modified in global config mode with 

   "fspf config vsan 1" or on interface level like
   " fspf [cost|dead-interval|hello-interval|passive|retransmit-interval]


- sh fspf [database|interface] [vsan]

- sh fcroute unicast vsan


Fabric Login (FLOGI)

- All initiators and targets must FLOGI before sending any data into the fabric

- Verification - sh flogi database vsan

- No configuration required

- No FLOGI indicates a basic link-level negotiation problem

- The FLOGI database is local to switch which means only directly connected devices 

    will show up, It's FCNS job to   progpogate this information to entire fabric


Fiber Channel Name Services

- FCNS (AKA Directory Services) keeps a mapping of FCIDs to WWPNs

- Analogous to IP ARP Cache in ethernet

- End devices register with the FCNS after FLOGI

- sh fcns database

- If Node did FLOGI but is not in everyone's FCNS, it indicates the Fabric is broken

> E.g. VSAN is isolated, EISL allowed list is wrong etc

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