IBM SAN Switch Question

Posted on 2005-05-08
Last Modified: 2013-11-15
Hi all,

My vendor did not create any zone for my SAN switch and all servers are already in production.
Now, i want going to create two zones and assign members to it, will i lost the data?
Is there any procedure i should follows?


Question by:patrick24
    LVL 12

    Accepted Solution

    Zones have effect on the data on the disks.   However, if you make a mistake in defining the zone, you could find that a server can no longer access one or more disks.  If this happens, the data is not lost...just disconnected.   Obviously, there is a lot of potential for disrupting production.  You should shut down all servers connected to the switch before making changes, and then start them up one by one, checking that each one has the correct disks available.  

    Why do you want to create zones?
    LVL 30

    Assisted Solution

    by:Duncan Meyers
    If you have redundant paths with two switches and failover software installed on the hosts then you will be able to zone each switch individually - carefully of course! If you have McData switches then the zoning take effect when you save and activate the zoning config. The switches don't seem to "blip" (or if they do it is only for a couple of mS) when you save/activate the new config. Brocade switches "blip" the ports when a new config is saved and the host failover software will kick in if there is active I/O on that path.

    >Why do you want to create zones?
    In short, it reduces "broadcast" FC traffic (mostly State Change Notices). If I remember correctly. Also, it isn't a good idea to have multiple initiators in the same zone.
    LVL 12

    Expert Comment

    Excuse me...that should have been "zones have *no* effect on the data on the disks."
    LVL 2

    Author Comment

    Thank guys,

    I know for hard zoning, we go by the port number but for soft zoning, do you guys use the WWNN or WWPN ? what the difference anyway?
    LVL 30

    Expert Comment

    by:Duncan Meyers
    The WWNN (World Wide Node Name) is the address that is phsically "burnt" on to the FC device (HBA for example) so it is analagous to a MAC address. The WWPN (WW Port Name) is assigned by the fabric (the FC switch) when the device logs in to the fabric (FLOGI - Fibre LOG In). The WWPN usually only differs by one bit. For example, WWNN of QLogic FC HBA's is 20:00... WWPN  is usually 21:00.... The full WWN is WWNN:WWPN - a full 128 bit disaster! To top that all off, once the server (or storage) has logged into the switch (and the end to end log-in a PLOGI) it is allocated a 24 bit ID that is used for FC conversations instead of the WWN.  

    In setting up soft zoning, I usually select the WWNN for the servers and the WWPN for the storage (I work with EMC kit a lot and the WWN's for the FC attached storage ports are WWPNs).

    In essence, you can use either WWPN or WWNN, but check with IBM as they may have their own zoning requirements.
    LVL 87

    Expert Comment


    No comment has been added to this question in more than 21 days, so it is now classified as abandoned..
    I will leave the following recommendation for this question in the Cleanup topic area:
    Split: Carlo-Giuliani, meyersd

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