Priority group activation - what if lowest priority group has less servers than the "less than" setting?

Further if we have an even lower priority group with 1 server (so:

• PG10 = 4 servers
• PG5 = 2 servers
• PG1 = 1 server

with activation set to "< 3").

When 2 servers fail in PG10, and PG5 is activated - since PG5 has less than 3 servers active right from the start, will PG1 also be activated?

Hi,

First scenario :

• Activation: less than 3 servers
• PG 2: 4 servers*
• PG 1: 2 servers

Based on this official article "If the number of available members in the highest priority group drops below the minimum number, the BIG-IP system also distributes traffic to the next higher priority group"

So 2 servers in PG2 goes down, traffic will be load balanced between the 2 remaining servers in PG 2 and both servers in PG 1.

You can also look at the following video from min 10 to the end it demonstrates this scenario.

https://www.youtube.com/watch?v=wzyhCh-2NqY

Second scenario :

• Activation: less than 3 servers
• PG10 = 4 servers (2 down 2 UP)
• PG5 = 2 servers (2 UP)
• PG1 = 1 server (UP)

When 2 servers fails in PG10, the less than 3 servers active in the highet priority group (PG10) is matched, the load balancer will look to the next highest priority group to have at least 3 servers active. At this point, PG10 has 2 servers UP and PG5 has 2 UP (a total of 4 servers are UP) then PG1 will not receive any traffic. If we loose all PG10 servers then PG5 and PG1 will receive traffic.

Regards

Hi

Priority group is simple.

The pool enable as much priority groups as required to satisfy defined minimum requirement.

If PG10 doesn't have enough available servers to satisfy minimum of 3 servers, pool will activate all members in PG5

Thank you guys - that's the key concept i didn't understand, that "less than 3" for activation isn't evaluated against a group per se, it simply means that at all times it's going to activate groups as needed until at least 3 servers are up. That's unambiguous.