Datalight Reliance Edge™ is the only embedded file system designed to capture and preserve decision-quality data with deterministic behavior required by today’s autonomous systems. A transactional file system, Reliance Edge protects critical system and user data from corruption, specifically for systems where power loss may occur.

Reliance Edge works with a broad array of storage media including: eMMC, SD/MMC, NVRAM, USB mass storage and SATA (or PATA) disks. When paired with a flash translation layer flash driver like FlashFX Tera, Reliance Edge delivers the functionality of a complete flash file system. As a small-footprint IoT file system, Reliance Edge builds upon and continues the Reliance file system legacy that is hundreds of millions of devices strong and is supported by Datalight’s award-winning support.



Transactional design never overwrites live data

Once the data is written, it is never in an indeterminate state

Writes are atomic

Meta data never points the wrong user data

Can be configured to use as little as 4 KB of RAM, 12 KB of code 

Ideal for resource-constrained environments

Tree-based metadata

Mounts quickly and consistently after unexpected shutdown/power loss

Works with any block device driver supporting HDD, RAM, USB Mass Storage, SD/MMC, or eMMC

Allows you to choose the best storage for your design

Ships as source code that is MISRA C:2012 compliant Design standard prevents many bugs; flexible for use case customization

MISRA C:2012 Design Assurance Package available to commercial licensees

Makes certification much easier; deterministic I/O enables planned system design

GPL v2 source version on github Enables easy evaluation and prototyping, along with personal use – more cost effective than creating your own file system

Simple Architecture

Quick and efficient implementation

Flexible File System Configuration

Reliance Edge provides three main options for file system configuration, detailed below. Each of these thread-safe options is also completely power fail safe, preserving file system structure and user data in the case of a power interruption. Flexible transaction point configuration is available in each case, and key file system operations are deterministic, providing unprecedented predictability.

Configuration Options
Full POSIX Small POSIX FSEssentials
API set POSIX-like POSIX-like
(not including rename)
Number of files Variable Variable Fixed
Number of volumes Multiple Multiple Multiple
Maximum stack depth 824 744 556
Buffers (minimum) 12 6 5
File references Names Names Numbers
Code size (ROM) 17.6 KB 16.7 KB 10.6 KB
RAM requirement 8.4 KB 5.3 KB 3.9 KB


This option includes path-based file access, file handles and atomic directory operations (including rename). 


This option contains the same POSIX-like APIs as above, but excludes rename.

File System Essentials

The File System Essentials API supports read, write and truncate on files referred to by a number, which is configured at compile time.

Reliance Edge Resources

Developers Guide
Licensing Options
 Kits Available For

The open source version of Reliance Edge is licensed under the terms of GNU General Public License, version 2.