Zram as SWAP file in Proxmox VE

Zram Technology

Zram is a technology which allows you to create a block device in RAM on which data is compressed by one of the selected algorithms when saving.

There are several algorithms available, depending on the version of the operating system. For example, in the latest Proxmox version, these are lzo, lz4, lz4hc, deflate. The default setting is lzo. This is probably because it was added to the kernel module earlier and saved as a default setting for compatibility purposes. The most optimal choice at the moment is lzo4, which has an optimal speed to compression ratio and is very fast to decompress. Furthermore, lz4 is available in almost all current linux distributions.

How to enable the zRAM module for faster swapping on Debian/Ubuntu

This example should work with recent versions of Debian (from version 9) and Ubuntu (from version 18). In this example we add 32G:

modprobe zram
zramctl -s 32G -a lz4 /dev/zram0
mkswap /dev/zram0
swapon /dev/zram0 -p 10

Next, set up automatic zram swap creation at system startup:

echo "zram" > /etc/modules-load.d/zram.conf
echo "zram" > /etc/modules-load.d/zram.confecho 'KERNEL=="zram0", ATTR { disksize } ="32G" RUN="/sbin/mkswap /dev/zram0", TAG+="systemd"' > /etc/udev/rules.d/99-zram.rules

echo "/dev/zram0 none swap defaults,pri=10 0 0" >> /etc/fstab

You can view the partition usage statistics by using the zramctl command without parameters:

zramctl

Example output:

NAME ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT
/dev/zram0 lz4 32G 48.7M 20.1M 21.5M 16 [SWAP]