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IoT Authors: Elizabeth White, Pat Romanski, Liz McMillan, William Schmarzo, Shelly Palmer

Related Topics: Cloud Computing, Security Journal, IT Strategy, Secure Cloud Computing, F5 Networks, Internet of Things Journal

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High Availability Groups on BIG-IP

High Availability of applications is critical to an organization’s survival.

On BIG-IP, HA Groups is a feature that allows BIG-IP to fail over automatically based not on the health of the BIG-IP system itself but rather on the health of external resources within a traffic group. These external resources include the health and availability of pool members, trunk links, VIPRION cluster members or a combination of all three. This is the only cause of failover that is triggered based on resources outside of the BIG-IP.

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.

In this scenario, there are three BIG-IP Devices – A, B, C and each device has two traffic groups on it.

ha1

As you can see, for BIG-IP A, traffic-group 1 is active. For BIG-IP B, traffic-group 2 is active and for BIG-IP C, both traffic groups are in a standby state. Attached to traffic-group 1 on BIG-IP A is an HA group which specifies that there needs to be a minimum of 3 pool members out of 4 to be up for traffic-group-1 to remain active on BIG-IP A. Similarly, on BIG-IP B the traffic-group needs a minimum of 3 pool members up out of 4 for this traffic group to stay active on BIG-IP B.

On BIG-IP A, if fewer than 3 members of traffic-group-1 are up, this traffic-group will failover.

So let’s say that 2 pool members go down on BIG-IP A. Traffic-group-1 responds by failing-over to the device (BIG-IP) that has the healthiest pool…which in this case is BIG-IP C.

ha2

Now we see that traffic-group-1 is active on BIG-IP C.

Achieving the ultimate ‘Five Nines’ of web site availability (around 5 minutes of downtime a year) has been a goal of many organizations since the beginning of the internet era. There are several ways to accomplish this but essentially a few principles apply.

  • Eliminate single points of failure by adding redundancy so if one component fails, the entire system still works.
  • Have reliable crossover to the duplicate systems so they are ready when needed.
  • And have the ability to detect failures as they occur so proper action can be taken.

If the first two are in place, hopefully you never see a failure. But if you do, HA Groups can help.

ps

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More Stories By Peter Silva

Peter is an F5 evangelist for security, IoT, mobile and core. His background in theatre brings the slightly theatrical and fairly technical together to cover training, writing, speaking, along with overall product evangelism for F5. He's also produced over 350 videos and recorded over 50 audio whitepapers. After working in Professional Theatre for 10 years, Peter decided to change careers. Starting out with a small VAR selling Netopia routers and the Instant Internet box, he soon became one of the first six Internet Specialists for AT&T managing customers on the original ATT WorldNet network.

Now having his Telco background he moved to Verio to focus on access, IP security along with web hosting. After losing a deal to Exodus Communications (now Savvis) for technical reasons, the customer still wanted Peter as their local SE contact so Exodus made him an offer he couldn’t refuse. As only the third person hired in the Midwest, he helped Exodus grow from an executive suite to two enormous datacenters in the Chicago land area working with such customers as Ticketmaster, Rolling Stone, uBid, Orbitz, Best Buy and others.

Writer, speaker and Video Host, he's also been in such plays as The Glass Menagerie, All’s Well That Ends Well, Cinderella and others.