Last week we talked about how
HA
Groups work on BIG-IP and this week we’ll look at how to configure
HA
Groups on BIG-IP.
To recap, an HA group is a configuration object you create and assign to a
traffic group for devices in a device group. An HA group defines health criteria
for a resource (such as an application server pool) that the traffic group uses.
With an HA group, the BIG-IP system can decide whether to keep a traffic group
active on its current device or fail over the traffic group to another device
when resources such as pool members fall below a certain level.
First, some prerequisites:
- Basic Setup: Each BIG-IP (v13) is licensed, provisioned and configured to
run BIG-IP LTM
- HA Configuration: All BIG-IP devices are members of a sync-failover device
group and synced
- Each BIG-IP has a unique virtual server with a unique server pool assigned
to it
- All virtual addresses are associated with traffic-group-1
To the BIG-IP GUI!
First you go to System>High Availability>HA Group List>and then
click the
Create button.
The first thing is to name the group. Give it a detailed name to indicate the
object group type, the device it pertains to and the traffic group it pertains
to. In this case, we’ll call it ‘
ha_group_deviceA_tg1.’
Next, we’ll click
Add in the Pools area under Health Conditions and add
the pool for BIG-IP A to the HA Group which we’ve already created. We then move
on to the minimum member count. The minimum member count is members that need to
be up for traffic-group-1 to remain active on BIG-IP A. In this case, we want 3
out of 4 members to be up. If that number falls below 3, the BIG-IP will
automatically fail the traffic group over to another device in the device group.
Next is HA Score and this is the sufficient threshold which is the number of up
pool members you want to represent a full health score. In this case, we’ll
choose 4. So if 4 pool members are up then it is considered to have a full
health score. If fewer than 4 members are up, then this health score would be
lower. We’ll give it a default weight of 10 since 10 represents the full HA
score for BIG-IP A. We’re going to say that all 4 members need to be active in
the group in order for BIG-IP to give BIG-IP A an HA score of 10. And we click
Add.
We’ll then see a summary of the health conditions we just specified including
the minimum member count and sufficient member count. Then click
Create HA
Group.
Next, we go to Device Management>Traffic Groups>and click on
traffic-group-1.
Now, we’ll associate this new HA Group with traffic-group-1. Go to the HA Group
setting and select the new HA Group from the drop-down list. And then select the
Failover Method to Device with the Best HA Score. Click
Save.
Now we do the same thing for BIG-IP B. So again, go to System>High
Availability>HA Group List>and then click the
Create button. Give
it a special name, click
Add in the Pools area and select the pool you’ve
already created for BIG-IP B. Again, for our situation, we’ll specify a minimum
of 3 members to be up if traffic-group-1 is active on BIG-IP B. This minimum
number does not have to be the same as the other HA Group, but it is for this
example. Again, a default weight of 10 in the HA Score for all pool members.
Click
Add and then
Create HA Group for BIG-IP B.
And then, Device Management>Traffic Groups> and click
traffic-group-1. Choose BIG-IP B’s HA Group and select the same Failover
method as BIG-IP A – Based on HA Score. Click
Save.
Lastly, you would create another HA Group on BIG-IP C as we’ve done on BIG-IP
A and BIG-IP B. Once that happens, you’ll have the same set up as this:
As you can see, BIG-IP A has lost another pool member causing traffic-group-1
to failover and the BIG-IP software has chosen BIG-IP C as the next active
device to host the traffic group because BIG-IP C has the highest HA Score based
on the health of its pool.
Thanks to our TechPubs group for the basis of this article and check out a
video
demo here.
ps
