How can I be alerted when an EBS instance is running out of space?

Question

I'm running a wordpress off of AWS, and I can't figure out how to monitor if the volume is running out of capacity. There are many options for monitoring other things, but I just want to know when we run low on space.

Answer 1

There are no built in metrics for disk space - Because Amazon is looking at this 'from the outside', they don't know what you've done with an EBS volume: it could be part of a raid set, formatted in some exotic format etc.

Amazon has a system called CloudWatch that can be used to monitor AWS systems and resources. Luckily, CloudWatch supports custom metrics: you can use the CloudWatch APIs to add any data you want (and then create alerts off them).

Amazon provides some sample scripts that will publish (among other things) disk space utilisation to Cloudwatch. Do be aware that there is a small charge associated with using custom metrics - $0.50 per metric per month.

Answer 2

I agree with Frederick Cheung's answer; however, I found this utility for Windows instances: http://www.eleven41.com/labs/cloudwatch-monitor-for-windows/. It runs as a service and will send the disk space and memory usage metrics to CloudWatch for you. From there, you'd just need to set up the alarm in CloudWatch.