AWS EC2 Instance right-sizing, more suitable instance types?

boog

1/26/24, 2:08 PM

I have some EC2 instances that are currently over-provisioned for cpu/mem. The problem I'm seeing in trying to right-size these instances is that a lot of them use barely any cpu and have a baseline of <5% cpu usage, however they need a reasonable amount of memory, perhaps 4gb of RAM.

We're currently using the T3 instance types, so theoretically many of these instances would do fine on nano or micro t3 instances, however they need more RAM than what's offered in those sizes. In other words, I don't think the T-series cpu and memory offerings scale correctly for our workloads.

Ideally, I would want instance types that offer low cpu baseline percentages, but with a reasonable amount of RAM (4gb at least).

I know there are memory optimized instance types, but these all offer a ton of RAM, way overkill for what we need.

Is there a better instance type for low cpu but a reasonable amount of memory? I don't want to keep them overprovisioned on CPU just to get the 4GB of memory on the T3 medium.

Maybe moving to ARM based cpu? Any ideas?

The problem originates from the last guy who worked here, who set every instance up as Server2019 desktop experience... for simple services that could run just fine headless/on server core or a small linux instance with barely any resource utilization... so now being unable to just switch over to server core without rebuilding, trying to right-size these has become problematic just to be able to support friggen windows desktop. Dumb.

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Tim

1/29/24, 6:30 PM

AWS T3 instances should be perfect for what you've described. I've copied a table from the page above into the image below, prices as at 2021-01-30. As you can see T3 instances can have up to 32GB RAM. T3a are AMD CPUs which are slightly cheaper than Intel.

The ways I can think of right now to go cheaper are :

Rewrite your software to work on AWS Lambda
Use AWS LightSail instances which can be cheaper in some cases than EC2
Use another provider, eg digital ocean

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boog

2/3/24, 4:35 PM

I guess, my problem with the t-series instances is that the cpu seems to be overpowered for the amount of RAM offered at each tier. For example, a normal Windows Server 2019 instance running basic AD stuff, domain controller, dns, dhcp- might utilize only between 1-5% of the cpu for a t3 medium, but you can't downsize because you need that 4gb of RAM. The general rule is if your baseline is at or below 40% utilization you can cut the server in half. The RAM offerings on t-series are too low to allow that even though the cpu utilization is almost nothing.

Tim

2/3/24, 8:05 PM

I guess your options are use the T series, AWS LightSail can be quite cheap, or use a different provider. There are many that are more flexible and / or cheaper. If I didn't work in AWS professionally I'd probably use Digital Ocean or similar for my own stuff. Oracle Cloud has a generous free tier.

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