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One of the easiest way of increasing the responsiveness of your server and guarding against out of memory errors in your applications is to add some swap space. Swap is an area on a hard drive that has been designated as a place where the operating system can temporarily store data that it can no longer hold in RAM.
Basically, this gives you the ability to increase the amount of information that your server can keep in its working “memory”, with some caveats. The space on the hard drive will be used mainly when space in RAM is no longer sufficient for data.
The information written to disk will be slower than information kept in RAM, but the operating system will prefer to keep running application data in memory and use swap for the older data. Overall, having swap space as a fall back for when your system’s RAM is depleted is a good safety net.
In this guide, we’ll cover how to create and enable a swap file on an Ubuntu 14.04 server.
Note
Although swap is generally recommended for systems utilizing traditional spinning hard drives, using swap with SSDs can cause issues with hardware degradation over time. Due to this consideration, we do not recommend enabling swap on DigitalOcean or any other provider that utilizes SSD storage. Doing so can impact the reliability of the underlying hardware for you and your neighbors.
If you need to improve the performance of your server, we recommend upgrading your Droplet. This will lead to better results in general and will decrease the likelihood of contributing to hardware issues that can affect your service.
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Former Senior Technical Writer at DigitalOcean, specializing in DevOps topics across multiple Linux distributions, including Ubuntu 18.04, 20.04, 22.04, as well as Debian 10 and 11.
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You’re missing a ‘p’ in this line:
sudo sysctl vm.swapiness=10
should be:
sudo sysctl vm.swappiness=10
I also noticed your fstab has ‘defaults’ under options, it should be ‘sw’ instead. It is the default debian/ubuntu option for swap. ‘defaults’ is a great option for your userspace filesystem, but not ideal for swap.
/swapfile none swap sw 0 0
Hi Brandon:
You’re absolutely right on both points. Those were oversights on my part. I’ve updated the article to reflect your suggestions.
how much swap should we create for a 1gb ram droplet? (size of swap file)
@chris: A general rule of thumb that people use is to have twice your memory in swap. So if you have 1 GB of RAM, you want 2 GB of swap. Though that was from back in the day when people didn’t have nearly as much memory as they usually do now. So 2 GB of swap is probably more than enough. If disk space is a concern, you can easily get away with 1 GB.
Nice article Justin. Is it absolutely necessary to have some swap (at least to begin with) when upgrading memory? If I have applications that mandate not to use swap. I set the swapiness to 0 on CentOS.
You’ve still got an error in the command:
sudo sysctl vm.swapiness=10
Should have another ‘p’:
sudo sysctl vm.swappiness=10
Helpful article. Thanks.
Ansible Automated version of this tutorial available @ http://greenycloud.com/adding-swap-to-digitalocean-droplets-or-any-vps-server-real-easy-way/
@scott: Very cool! Thanks for sharing that.
Swap memory should appear on Virtualmin System information page as Virtual memory ?
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