T2 instances are Burstable Performance Instances that provide a baseline level of CPU performance with the ability to burst above the baseline. The baseline performance and ability to burst are governed by CPU Credits. Each T2 instance receives CPU Credits continuously at a set rate depending on the instance size. T2 instances accrue CPU Credits when they are idle, and use CPU credits when they are active. T2 instances are a good choice for workloads that don’t use the full CPU often or consistently, but occasionally need to burst (e.g. web servers, developer environments and small databases).
In this post i will show how to make a installation of Redmine in AWS with some nice tools from AWS (EC2, RDS, S3, SES, ElastiCache) and making it auto scalable.
Amazon Simple Email Service (Amazon SES) is a highly scalable and cost-effective bulk and transactional email-sending service for businesses and developers. Subscription is quick and is on pay-as-you-go basis.
Sometimes EC2 CloudWatch monitoring shows 100% CPU usage but when you ssh to your instance and try to see it with ‘top’ you can’t understand what is happening. Probably, Amazon is “borrowing” some of your CPU cycles to give to someone else who needs it – this is standard practice for a virtualised environment where physical server resources like RAM usage and CPU cycles are often hugely over-committed.
To check for CPU steal, run top and take a look for the %st value. If this value is anything other than zero, it means your VM’s CPU cycles are being “borrowed”.
In case you lose your Amazon EC2 SSH Key, and can’t login in your instance. This isn’t a big problem if your instance is EBS based and you use an Elastic IP.
1. Upload your new SSH Key, or use one made by AWS
2. Make an AMI of your instance
3. Launch a new machine from your AMI, select the new SSH Key
4. Log in your machine with default user (ubuntu, ec2-user, depends on your original AMI image)