Understanding and Increasing SWAP Memory in KVM Virtualization Linux VPS
SWAP memory acts as an extension of your RAM, kicking in when your RAM is fully utilized. When your RAM runs out of space, additional data is moved to the SWAP memory on your hard disk. In this guide, we'll walk you through the steps to modify and increase SWAP memory on our KVM virtualization Linux VPS packages.
How Much SWAP Memory Should You Have?
There’s no one-size-fits-all answer to this question. Some suggest your SWAP should be half the size of your RAM, while others recommend it match or exceed your RAM size. For this guide, we’ll assign 6 GB of SWAP memory.
Steps to Allocate SWAP Memory
1. Check Existing SWAP Memory
Start by verifying whether your server is currently using any SWAP memory with the following command:
free -h
The output will show two lines: "Mem" and "Swap", reflecting your server’s RAM and SWAP memory. The "Swap" line should display zeros if no SWAP memory is in use.
2. Allocate 6 GB of SWAP Memory
To allocate 6 GB of disk space for SWAP memory, use:
fallocate -l 6G /swapfile
You can verify the allocation with:
ls -lh /swapfile
If you see something like -rw-r--r--, you’ll need to adjust the permissions.
3. Change File Permissions
Set the correct permissions for the swapfile:
chmod 600 /swapfile
Confirm the change:
ls -lh /swapfile
You should now see -rw------- for the swapfile.
4. Set Up the Swap Area
Mark the swapfile as a Linux swap area:
mkswap /swapfile
5. Enable SWAP Memory
Activate the SWAP memory with:
swapon /swapfile
Verify the setup by running:
free -h
The "Swap" line should now show 6 GB.
Making SWAP Memory Permanent
After a reboot, your SWAP settings may reset. To make them permanent, follow these steps:
1 Backup and Edit /etc/fstab
First, back up the existing fstab file:
cp /etc/fstab /etc/fstab.old
Then, add the SWAP configuration to fstab:
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
Additional SWAP Memory Options
1. Swappiness
Swappiness determines how frequently your system moves data to the SWAP file. It ranges from 0 to 100. Lower values (like 10) keep more data in RAM, while higher values move data to SWAP more often. Check the current value with:
cat /proc/sys/vm/swappiness
2. VFS Cache Pressure
This setting controls how aggressively the system reclaims memory used by the filesystem cache. The default is 100, but lowering it to 50 can be beneficial. Check the current setting with:
cat /proc/sys/vm/vfs_cache_pressure
To modify these options, edit the /etc/sysctl.conf file and add:
vm.swappiness=10
vm.vfs_cache_pressure=50
If you have any questions, feel free to reach out to our customer support team. We're here to help!
