←back to thread

Replacing a $3000/mo Heroku bill with a $55/mo server

(disco.cloud)
804 points jryio | 5 comments | 21 Oct 25 20:28 UTC | HN request time: 0.001s | source
Show context
speedgoose ◴[21 Oct 25 21:12 UTC] No.45661785[source]▶
Looking at the htop screenshot, I notice the lack of swap. You may want to enable earlyoom, so your whole server doesn't go down when a service goes bananas. The Linux Kernel OOM killer is often a bit too late to trigger.

You can also enable zram to compress ram, so you can over-provision like the pros'. A lot of long-running software leaks memory that compresses pretty well.

Here is how I do it on my Hetzner bare-metal servers using Ansible: https://gist.github.com/fungiboletus/794a265cc186e79cd5eb2fe... It also works on VMs.

replies(15): >>45661833 #>>45662183 #>>45662569 #>>45662628 #>>45662841 #>>45662895 #>>45663091 #>>45664508 #>>45665044 #>>45665086 #>>45665226 #>>45666389 #>>45666833 #>>45673327 #>>45677907 #
levkk ◴[21 Oct 25 21:51 UTC] No.45662183[source]▶
Yeah, no way. As soon as you hit swap, _most_ apps are going to have a bad, bad time. This is well known, so much so that all EC2 instances in AWS disable it by default. Sure, they want to sell you more RAM, but it's also just true that swap doesn't work for today's expectations.

Maybe back in the 90s, it was okay to wait 2-3 seconds for a button click, but today we just assume the thing is dead and reboot.

replies(16): >>45662314 #>>45662349 #>>45662398 #>>45662411 #>>45662419 #>>45662472 #>>45662588 #>>45663055 #>>45663460 #>>45664054 #>>45664170 #>>45664389 #>>45664461 #>>45666199 #>>45667250 #>>45668533 #
bayindirh ◴[21 Oct 25 22:15 UTC] No.45662411[source]▶
This is a wrong belief because a) SSDs make swap almost invisible, so you can have that escape ramp if something goes wrong b) SWAP space is not solely an escape ramp which RAM overflows into anymore.

In the age of microservices and cattle servers, reboot/reinstall might be cheap, but in the long run it is not. A long running server, albeit being cattle, is always a better solution because esp. with some excess RAM, the server "warms up" with all hot data cached and will be a low latency unit in your fleet, given you pay the required attention to your software development and service configuration.

Secondly, Kernel swaps out unused pages to SWAP, relieving pressure from RAM. So, SWAP is often used even if you fill 1% of your RAM. This allows for more hot data to be cached, allowing better resource utilization and performance in the long run.

So, eff it, we ball is never a good system administration strategy. Even if everything is ephemeral and can be rebooted in three seconds.

Sure, some things like Kubernetes forces "no SWAP, period" policies because it kills pods when pressure exceeds some value, but for more traditional setups, it's still valuable.

replies(8): >>45662537 #>>45662599 #>>45662646 #>>45662687 #>>45663237 #>>45663354 #>>45664553 #>>45664705 #
vasco ◴[21 Oct 25 22:45 UTC] No.45662687[source]▶
In EC2 using any kind of swapping is just wrong, the comment you replied to already made all the points that can be made though.
replies(1): >>45662758 #
1. bayindirh ◴[21 Oct 25 22:53 UTC] No.45662758[source]▶
From my understanding, the comment I'm replying to uses EC2 example to portray that swapping is wrong in any and all circumstances, and I just replied with my experience with my system administrator hat.

I'm not an AWS guy. I can see and touch the servers I manage, and in my experience, SWAP works, and works well.

replies(1): >>45662999 #
2. matt-p ◴[21 Oct 25 23:16 UTC] No.45662999[source]▶
Just for context EC2 typically uses network storage that, for obvious reasons, often has fairly rubbish latency and performance characteristics. Swap works fine if you have local storage, though obviously it burns through your SSD/NVME drive faster and can other side effects on it's performance (usually not particularly noticeable).
replies(1): >>45667245 #
3. bayindirh ◴[22 Oct 25 10:50 UTC] No.45667245[source]▶
Thanks, I'll keep that in mind if I start to use EC2 for workloads.

However, from my experience, normal (eviction based) usage of SWAP doesn't impact the life of an SSD in a measurable manner. My 256GB system SSD (of my desktop system) shows 78% life remaining after 4 years of power on hours, which also served as /home for at least half of its life.

replies(1): >>45674697 #
4. vasco ◴[22 Oct 25 20:24 UTC] No.45674697{3}[source]▶
You don't care about life of any hardware in the cloud, that doesn't really matter either unless you work for the cloud provider in their datacenter teams.
replies(1): >>45679358 #
5. bayindirh ◴[23 Oct 25 07:54 UTC] No.45679358{4}[source]▶
Yes, but I care about hardware life on my own personal systems and infrastructure I manage, so... :)