ZRAM is a compressed block device that lives in RAM. It allows the system to store data in memory in a compressed form instead of pushing it to disk swap.

In simple terms:

• It acts like swap
• But stays in RAM
• And compresses data to fit more

This means faster access times and less reliance on slow disk I/O.

Table of Contents

The Problem

I’m running my docker mail stack and Pangolin Reverse Proxy, this eats up RAM when a high volume of email hits the server and the RSPAM evaluate the email sents. And also from traffic forwarded by my local servers going to the Pangolin Reverse Proxy - an upgrade would be the absolute fix but ZRAM would slightly help with the RAM shortage.

Setup

Install

1sudo apt update
2sudo apt install zram-tools

Configuration

Edited the default configuration file.

1sudo vim /etc/default/zramswap

Then set:

1ALGO=lz4
2PERCENT=75
3PRIORITY=100

• ALGO=lz4 - fast compression (recommended)
• PERCENT=75 - ZRAM = 75% of RAM
• PRIORITY=100 - higher than disk swap

Other compression algorithms.

Restart service.

1sudo systemctl restart zramswap

Verify

ZRAM device /dev/zram0 is created.

1fdisk -l | grep zram
2Disk /dev/zram0: 721.13 MiB, 756154368 bytes, 184608 sectors
3Units: sectors of 1 * 4096 = 4096 bytes
4Sector size (logical/physical): 4096 bytes / 4096 bytes
5I/O size (minimum/optimal): 4096 bytes / 4096 bytes

1zramctl 
2NAME       ALGORITHM DISKSIZE  DATA  COMPR TOTAL STREAMS MOUNTPOINT
3/dev/zram0 lz4         721.1M  2.8M 884.4K  2.4M       1 [SWAP]
4
5zramctl --output-all
6NAME       DISKSIZE  DATA  COMPR ALGORITHM STREAMS ZERO-PAGES TOTAL MEM-LIMIT MEM-USED MIGRATED MOUNTPOINT
7/dev/zram0   721.1M  2.8M 884.4K lz4             1         59  2.4M        0B     2.4M       0B [SWAP]

1swapon --show
2NAME       TYPE        SIZE   USED PRIO
3/dev/vda3  partition   512M 310.8M   -2
4/dev/zram0 partition 721.1M   2.7M  100

Swappiness

Adjust how aggressively Linux swaps.

1sysctl vm.swappiness=80

Make it persist even after reboot.

1echo "vm.swappiness=80" | sudo tee -a /etc/sysctl.conf

Higher value means more use of ZRAM.