Long vs short (terminated) running spot instances with similar pricing histories

1
votes

I have had some spot instances run for months which was expected based on the spot price history which was relatively flat and I have had other instances get terminated within an hour typically even though the pricing history looked similar (low and flat) to the long running instances and my bidding price was well above the on-demand price.

How is this behavior explained as I would expect a visible price hike in the spot pricing to determine whether the request was terminated?

Also are there any resources out there to determine the reliability of spot instances beyond the spot pricing history provided in the console as this seems to not tell the whole story?

2
amazon-web-servicesamazon-ec2
That is the tricky part of spot, unfortunately AWS has more control on these instances than us. I don't think they will reveal "why" instance terminated. You just need to be ready to have a backup upon termination notice. – INVOKE Cloud
Was hoping an AWS rep could give me a solid answer though I am guessing this is something they don't want to share as if you could run a spot instance for months on end, it would just get people to just turn to spot vs on demand... – Cobman
Yeah, some of those could be implementation details which they don't want to expose. – INVOKE Cloud

2 Answers

0
votes

I have found that that m series instances tend to stay on longer than the c series instances even though the pricing looks totally flat for both. Guessing it is because people use c series for more batch processing workloads but still doesn't explain why c series pricing is so flat. I would have thought that by boosting the bid price way high, one could avoid getting terminated.

0
votes

I would recommend using the AWS spot instance advisor tool before selecting an instance type. This tool gives you information on the frequency of termination of various instance types that can help your case. Preferably go for instances that have less than 5% rate of termination.

P.S. The tool helps you select the best available spot instance type base on your infrastructure requirements vs costs vs frequency of termination tradeoff