NIC heartbeat / I/O fensing - Veritas Cluster Server

This is a discussion on NIC heartbeat / I/O fensing - Veritas Cluster Server ; Hello All, I have configured two - two nodeclusters. I am using 4 heart beat NIC's. But I haven't configured any quorum disk or I/O fensing. The cluster is working fine. My question is having 4 heartbeat channels is sufficient ...

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Thread: NIC heartbeat / I/O fensing

  1. NIC heartbeat / I/O fensing


    Hello All,

    I have configured two - two nodeclusters. I am using 4 heart beat NIC's.
    But I haven't configured any quorum disk or I/O fensing. The cluster is working
    fine. My question is having 4 heartbeat channels is sufficient or should
    I go for quorum disk and / or I/O fensing.

    thanks
    Biju..

  2. Re: NIC heartbeat / I/O fensing

    VCS 4.1 and later supports SCSI III PGR (Persistent Group Reservations)
    also known as I/O fencing.

    Basically, if your hardware supports it (and most modern arrays do), you
    can protect your data.

    Let me give you an example:

    Say you have 2 nodes in a cluster. They both can see 10 disks on the
    SAN. The disks all belong to a single diskgroup and the idea is that
    only 1 should be able to import this diskgroup and start Oracle and read
    the database on the disks.

    The biggest problem is that BOTH the machines can see the disks. You get
    a new admin. who does not know that you're using VCS to control the
    database to be on either of the 2 machines. The new admin sees the
    disks, sees that the disks belong to a diskgroup (vxdisk -o alldgs list)
    and then imports the diskgroup on the other machine (while the one
    machine has still got it imported. OOPS !!!


    The same can happen if you lose all heartbeats between nodes in a
    cluster and someone forces a node to start (by auto enabling service
    groups).


    The way to protect against this, is by usnig I/O fencing.
    The machine that imports the diskgroup (via VCS) will place reservation
    keys on the disks. This will prevent other machines from being able to
    write to the disks.

    SO, I/O fencing is just another protection method to try to prevent data
    .. The human factor is mostly responsible for messing up data (can not
    remember percentages, but a lot is still human error).


    So, in answer to your qestion, no you don't need fencing. It is very
    good to protect at all costs against data loss, but it is better to make
    sure the admins for the machine(s) know what they're doing.

    Biju K Joseph wrote:
    > Hello All,
    >
    > I have configured two - two nodeclusters. I am using 4 heart beat NIC's.
    > But I haven't configured any quorum disk or I/O fensing. The cluster is working
    > fine. My question is having 4 heartbeat channels is sufficient or should
    > I go for quorum disk and / or I/O fensing.
    >
    > thanks
    > Biju..


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