High Availability

High Availability

VM HA monitors the esx failure – if any failure happens the VM in it are restarted in another host in the cluster.

1. Decrease downtime and improve the availability
2. It takes at least 3 min to power up the VM in another host
3. Ping 1 sec once to another esx
4. If 15 sec fails it assumes it is dead

Procedure

1. HA

   - 1.1-host monitoring status

   - 1.2-admission control [allow / disallow]

   - 1.3-Admission control policy

        1.3.1=> Host failure tolerates [1]

      1.3.2 => % of cluster resource reserved for failover spare capacity [25 %]

      1.3.3 => specifies a failover host [^]

 2. CLUSTER DEFAULT SETTING

         - 2.1 => VM restart priority

         - 2.2 => host isolation response

3. VM MONITORING

     - 3.1 => VM Monitoring Status [enable / not]

    - 3.2 => default cluster setting 

Monitoring Sensitivity [low --- High] [HA will restart VM if the heartbeat between the host and the VM has not been received within a 30 second interval. HA restarts the VM after each of the first 3 failures every hour]

 4. EVC

 5. SWAP file location

How HA works

• First 5 hosts are primary hosts then all subsequent hosts are secondary hosts.
• The very first host is the primary master
• Usually VC communicates to primary master
• Primary master maintain and replicate the cluster info to all the hosts.
• Primary master – decides where to restart the VM

                                               - keeping track of failed restart attempt

                                               - determining when it is appropriate to keep trying to restart the VM

•  If VCenter down, HA will work because the configuration stored in the aam folder of the ESX. Only DRS won’t work

List primary hosts: 

$ cat /var/log/vmware/aam/aam_config_util_listnodes.log 

Secondary host promoted after primary is: • maintenance mode • disconnected • removed - not on failure

Host isolated: no heartbeat for 12 seconds, then cannot ping isolation addresses. Isolation response: • Power off • Leave powered on • Shut down (default). However Host Failure is only after 1 5 seconds.

Admission Control types:

• Host

• Resource Pool

• HA (only HA admission control can be disabled)

Admission Control:

Rules if VMs can power on when they violate availability constraints at HA failover. Actions that change a reservation must satisfy admission control.

HA Admission Ctrl policies:

Host Failures Cluster Tolerates (1 -4 hosts),

 % of Cluster Resources (up to 50%),

 Specify a Failover Host.

  Policy Factors

   • Resource fragmentation

   • Flexibility

   • VM diversity

Slot size: represents VM CPU & memory resources needed for any powered on VM. Distorted by large VM reservations. Avoided with advanced attributes das.slotCpuInMHz or das.slotMemInMB

• Slot size :- maximum resource of a VM
• Admission control: checks the resource availability- if success allows to start the VM.
• Affinity rules : keep the specified VM’s together or separate the VM

- Incoming port: TCP/UDP 8042-8045 - Outgoing port: TCP/UDP 2050-2250

Config file is

1. /opt/vmware/aam

2. /opt/vmware/aam /bin/….

3. /opt/LGT0aam512/config/*

Logs:

 HA logs: /var/log/vmware/aam/ aam_config_util_*.log

Service

  #service vmware-aam stop 

To install and uninstall the HA agent

    1. /opt/vmware/aam/bin/vmware-aam-ha-uninstall.sh

    2. #rm –rf /opt/vmware/aam

  Log files>>>>>>>> /opt

          - /opt/vmware