Does Discourse scale well with cores?

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Scaling Discourse with Cores

The discussion revolves around the impact of core count on Discourse performance. merefield shares their experience with 2-core, 2 GB RAM VPSs and wonders if a 1-core server would be handicapped in comparison. tophee notes that the number of simultaneously active users, not sites, is the key factor in performance.

merefield asks if doubling cores can serve twice as many users, assuming I/O can handle it. cpradio suggests that downgrading a dev instance to 1 core is feasible, as low traffic wouldn’t warrant a more powerful setup. They share their own experience with a 1-core, 1 GB RAM dev server, which doesn’t feel sluggish.

fzngagan provides a link to a relevant discussion on the impact of CPU speed on Discourse performance. Overall, the consensus seems to be that a 1-core server can be sufficient for smaller and dev sites, but may not be ideal for larger production sites.

1

Guys, running 3 Discourse sites (one is dev!) on 2 Core, 2 GB RAM VPSs with zero issues and excellent performance … but I wondered:

  • Does a 1 Core server handicap performance in comparison?
  • What processes make use of the extra cores when available?
  • Do extra cores help serve more web requests at the same time?

For smaller and dev sites, does scaling down to 1 core make sense?

Has anyone graphed CPU use on a busy server?

2

If you’re using multi-site install, my understanding is that the number of sites barely matters, what counts is the number of simultaneously active users on all sites.

3

Yeah, so performance does scale with cores?

You can serve ~twice as many users at once with double the cores? (assuming I/O can handle it)

No point in having low load dev server on a 2 core server?

(personally not running multi-site … they are all on virtually ‘discrete’ instances).

4

If you are simply asking if you can downgrade your dev instance, the answer is yes. You likely will never have enough active traffic to warrant the same setup you have for your active production sites.

For comparison purposes, my sandbox/dev site is a 1 core 1 GB RAM box on a 25 GB SSD and when I’m using it, it doesn’t feel sluggish to me at all. Rebuilds can take 15-30 minutes (since it is a full-fledge docker setup – not sure if you used the dev setup or official docker setup, but I imagine it will work with those specs for either).

5

This one might be of some help