When to upgrade T2 instances on AWS – CPU usage

AWS currently offers five levels of T2, Burstable Performance, instances on EC2. T2 instances “provide a base level of CPU performance with the ability to burst above the baseline.”

What’s not obvious from the general documentation page is that what’s the easy indicator to determine if you need to upgrade your T2 instance to the next level.

T2 Instance CPU Baseline Performance

What I found to be the best/quickest way to figure out when to upgrade T2 instance is to look at CPU Utilization (Percent) chart on the monitoring section for the instance. You need to compare the average usage of the CPU and the baseline of the T2 instance (above the baseline means the server is in the “burst” mode which uses the extra CPU credits).

Here are the baseline of each T2 instances:

Instance TypeCPU Baseline Performance
t2.nano5%
t2.micro10%
t2.small20%
t2.medium40%
t2.large60%

CPU Credit Usage and CPU Credit Balance

CPU credit usage chart and CPU credit balance chart are also good indicators. However, when the credit usage is too rapid, you might not be able to catch the issue in time to resolve the performance issue. The decrease in the credit balance is recorded only AFTER the server is performing beyond baseline performance. In other words, it’s not a good PREVENTATIVE indicator.

But Beware…

This is a simple way to measure the performance of the server reflected on CPU usage. There are other resources that causing the issue on your server(s). The most common issue I experience is the depletion of available memory. This happens if I am running a multiple servers (such as LAMP) under one instance. While CPU usage is within a normal range, not too uncommon to run out of available memory and your application stop running properly. I find that t2.nano instance and t2.micro instance aren’t sufficient to run a LAMP in most cases.

Resources: New Low Cost EC2 Instances with Burstable Performance
Resources: EC2 Update – T2.Nano Instances Now Available
Resources: Burstable Performance Instances

Make PHP Mail() work in AWS EC2 – Ubuntu 14.04

AWS IP addresses can be problematic for setting an email server in an EC2 instance…even with right setup email sent from the IP address can be marked as spam.

So what to do with setting up SMTP for your web applications? One alternative is to use AWS SES service. I decided not to use SES, however, because 1) each email address or domain needs to be approved and 2) there is cost associated with number of email sent out. These aren’t too bad of the restrictions but I wanted something that JUST work without configuring every time I build a website.

I went with MSMTP to use my gmail account to send email message by default. I can also overwrite the smtp setting per linux account. So if I were to host sites that are not mine, they can use their own smtp setup.
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