Keeping the lights on

Having spent years running 24×7 internet-facing production systems, I find that the monitoring element of an application delivery environment is often the last item to be addressed and built outside of the application delivery architecture. As we continue to build our application delivery infrastructure in the cloud, having a good monitoring strategy will allow us to arm ourselves with the information we need to make intelligent decisions.

So exactly what should be monitored?

Availability

The first element in a monitoring strategy is to determine whether the application is accessible. The most simplistic form of determining availability is ping. However, as most applications are obscured behind a load balancer, a ping response doesn’t necessarily mean that the application is responding to requests. Use a monitoring system that can speak application-layer protocols to ensure that the application is indeed healthy and responding to user requests. It’s best to leverage a 3rd party solutions that can assess availability from multiple networks and provide an unbiased view on the availability of the application.

Resource Utilization / Load

Next element in a good monitoring strategy is to determine how healthy a system is. Tracking the load of various system components will enable us to uncover bottlenecks within the application delivery environment. Leverage SNMP to capture and record utilization statistics on CPU, memory, disk IO, network IO, threads, and so on. Graph these stats to establish baseline and find correlations between each monitored element. (more…)

Making the case for a virtualized hardware appliance

As Data Center infrastructures become more virtualized, the desire for virtualized network services increases. We see 2 types of offerings:

1. virtual appliances delivered in a VM image, such as the Netscaler VPX from Citrix
2. hardware appliances that can be virtualized, such as Cisco ACE or ASA

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Another Amazon EC2 story

Looks like HotPads.com has abandoned traditional hosting and moved into Amazon’s elastic compute cloud (EC2). This is a trend that I’ve been following in the web space. (more…)

clustering versus load-balancing

Seems that often times the concept of clustering is often mixed up with that of load-balancing. I thought I’d quickly write something up to help clarify the difference between the two.

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Load Balancing Email

Here’s a different approach on using DNS to distribute users across multiple email servers. Load Balancing Email

local & global load balancing on the cheap

Not many people know what LVS is. I ran World Health Organization’s public website (www.who.int) using a pair of Compaq DL360 servers running Linux Virtual Server, which is an open-source load-balancer. And guess what, during SARS, we saw over 14 million hits a day at the peak. While I don’t have the specific cps / concurrent conn numbers (we didn’t measure those), the boxes did just fine. (more…)