ZRAM Compressed Memory — Tiered Swap Manager

A smart swap manager for Unraid that combines compressed RAM (ZRAM) with optional disk overflow protection. Helps memory-constrained servers avoid OOM crashes.

How It Works

Tier 1: ZRAM Swap (always active)
  Compressed in RAM — fast, ~3:1 ratio
  8 GB server → effectively ~20 GB usable memory

Tier 2: Disk Swap File (optional)
  Overflow to a writable disk when ZRAM fills (NVMe/SSD recommended)
  Prevents OOM — the kernel handles overflow automatically via priority

Features

• Auto-Sizing: Automatically sizes ZRAM to a percentage of your RAM (configurable 25-75%, default 50%).
• Live Dashboard Card: Real-time stats — RAM saved, compression ratio, CPU load, and a 1-hour history chart.
• Disk Overflow Protection: Optional swap file on any allowed mount (NVMe/SSD recommended; HDD permitted with a warning) for when ZRAM fills up. Includes a drive picker with smart media detection.
• Device Isolation: Labels all managed devices. Only shows its own ZRAM — won't interfere with other plugins that use ZRAM.
• Safe Operations: OOM evacuation checks before removing swap. Atomic config writes. CSRF protection on all actions.
• Boot Persistence: Automatically recreates your swap configuration on every boot.
• Compression Choice: Support for all kernel-supported algorithms (zstd, lz4, lzo, etc.).

Installation

Community Applications (Recommended)

Search for "ZRAM Compressed Memory" in the Apps tab.

Manual URL

Copy and paste into Plugins > Install Plugin: https://github.com/johnpwhite/unraid-plugin-zram/raw/main/unraid-zram-card.plg

Settings Guide

Tier 1: ZRAM Swap

• Size: Auto (percentage of RAM) or a fixed size like 4G.
• Auto Size Slider: 25-75% of physical RAM. Default 50%. Shows calculated size in real-time.
• Algorithm: zstd recommended (best compression ratio with good speed).
• Swappiness: 0-200 (kernel 5.8+ range). Default 150, recommended for ZRAM systems — tells the kernel that compressed-RAM swap is cheaper than dropping page cache. Use 100 for legacy parity, 180+ for aggressive zram with disk swap as fallback.

Tier 2: Disk Swap File

• Drive Picker: Shows eligible mounted filesystems with smart classification:
  • NVMe: Recommended (green)
  • SATA SSD: OK (green)
  • HDD: Not recommended (orange warning)
  • USB/Removable: Hidden
  • Btrfs RAID: Warned (swap files not supported on multi-device btrfs)
• Size: Configurable. 16 GB default.
• Priority: Automatically set to 10 (ZRAM is 100). Kernel uses ZRAM first, overflows to the disk tier only when needed.

Plugin Settings

• Refresh Interval: Dashboard update frequency (default 3000ms).
• Collection Interval: Background history recording frequency (default 3s).
• Debug Mode: Detailed logging for troubleshooting.
• Command Console: Real-time log of all plugin actions.

Requirements

• Unraid 6.12.1 or newer (optimized for Unraid 7.2+).
• ZRAM kernel module (standard in Unraid).
• For Tier 2: A writable mount under /mnt/cache or /mnt/disks with a supported filesystem (XFS, ext4, or single-device btrfs). NVMe/SSD recommended; HDD permitted but slower.

Created by John White