HA - Diskheartbeat

!!! In PowerHA 7.1 and later there is no disk heartbeat anymore. !!!
!!!  Below document is valid only for old HACMP configurations.  !!!




Disk Heartbeat

Heartbeat disks should be used in enhanced concurrent mode. Enhanced concurrent mode disks use RSCT group services to control locking, thus freeing up a sector on the disk that can now be used for communication. This sector, which was formerly used for SSA Concurrent mode disks, is now used for writing heartbeat information.

Any disk that is part of an enhanced concurrent volume group can be used for a diskhb network, including those used for data storage. Also, the volume group that contains the disk used for a diskhb network does not have to be varied on.

An enhanced concurrent volume group is not the same as a concurrent volume group (which is part of a concurrent resource group), rather, it refers to the mode of locking by using RSCT.


DISK HEARTBEAT:

lspv | grep hb            <--shows the actual state of heartbeat disks
cltopinfo -i | grep hb    <--shows what had been saved into the configuration (we have to change it to show the actual state)


Configuring from scratch

After the disk heartbeat VGs are ready (enhanced concurrent, should be varied off: mkvg -C ...), there are 2 methods for configuring
(there could be problems with Discovery method so Pre-Defined is suggested )

-PRE-DEFINED DEVICES METHOD: Manually have to to create a diskhb network first, then assign the disk-node pair devices to the network

    1. Create diskhb network
    Extended Configuration->Extended Topology->Configure HACMP Networks->Add a Network...
        choose:diskhb

        * Network Name                                       [anything you want]
        * Network Type                                        diskhb


    2. Add device
    Extended Configuration->Extended Topology->Configure HACMP Comm. Interfaces/Dev.->Add ...
        Add Pre-defined...
        Communication Devices
        Choose your diskhb Network Name

        * Device Name                                         [aix41_diskhb2] <--choose a unique name
        * Network Type                                        diskhb
        * Network Name                                        net_diskhb_aix41_aix42
        * Device Path                                         [/dev/vpath4]
        * Node Name                                           [aix41]

    You will repeat this process for the other node and the other device. This will complete both devices for the diskhb network.

(-VERIFICATION AND SYNCHRONIZATION: After configuring you can do: Extended Config.->Extended Verification ... (with default settings))


or:
-DISCOVERY METHOD: let the HA find it for us

    1. Run Discovery
    Extended Configuration->Discover HACMP-related Information from Configured Nodes
    (This will run automatically and create a clip_config file that contains the information it has discovered)

    2. Add device
     Extended Configuration->Extended Topology->Configure HACMP Comm. Interfaces/Dev.->Add ...
        Add discovered ...
        Communication Devices

        Choose appropriate devices (ex. vpath0 and vpath3)
        Select Point-to-Point Pair of Discovered Communication Devices to Add (one or more items can be selected (F7))


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Testing disk heartbeat:

DO NOT PERFORM THIS TEST WHILE HACMP IS RUNNING???

dhb_read -p devicename        <--dump diskhb sector contents
dhb_read -p devicename -r     <--receive data over diskhb network
dhb_read -p devicename -t     <--transmit data over diskhb network


1. on one node set receiving::
/usr/sbin/rsct/bin/dhb_read -p hdisk2 -r

2. on the other node set transmit:
/usr/sbin/rsct/bin/dhb_read -p hdisk2 -t


dhb_read -p rvpath0 -r <--Note: That the device name is raw device as designated with the "r" proceeding the device name.

If everything is OK: Link operating normally

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Monitoring disk heartbeat:

root@aix41: / # lssrc -ls topsvcs
Subsystem         Group            PID     Status
 topsvcs          topsvcs          921638  active
Network Name   Indx Defd  Mbrs  St   Adapter ID      Group ID
VLAN200_10_20_ [ 0] 2     2     S    10.10.10.2      10.10.10.2
VLAN200_10_20_ [ 0] en11             0x41c64107      0x41c64108
HB Interval = 1.000 secs. Sensitivity = 10 missed beats
Missed HBs: Total: 0 Current group: 0
...