WORM stands for “Write Once, Ready Many.” It is a data storage technology that allows data to be written to a storage device once and then be read multiple times. Importantly, that data cannot be overwritten, erased, or altered in any way.

Once stored on a WORM-compliant device, data becomes immutable, i.e., only authorized users can read it and nobody can change it. By rendering data immutable, WORM prevents bad actors from erasing or modifying critical data after it’s been stored—and prevents teams from accidentally doing the same.

This makes WORM highly advantageous for industries that are subject to strict data compliance requirements, including finance, healthcare, legal, government, and archiving. WORM ensures sensitive records are stored in a secure, immutable format that is compliant with regulatory requirements. Additionally, WORM functionality proves valuable for the distribution of copyright-protected data, such as PC and console games.

There are four forms of WORM implementations, which are often used alongside other data storage technologies to ensure data integrity and longevity.

True/Physical WORM: on traditional tape drives that are never-ever erasable

Hardware WORM: on a flash controller through an activated e-Fuse bit

Firmware-Extension WORM: in the firmware on a flash controller

Software WORM: on the host OS

True/physical WORM is the original technology, where WORM is implemented on tape drives.

Data is written to a tape with a specialized photosensitive coating. The tape is then heated by a laser, changing the physical state of the coating and permanently writing the data to the tape. Once “burned” to the tape, the data can never be erased, modified, or overwritten.

Software WORM is most often implemented in large-scale server settings.

Typically, software WORM attaches storage drives to a host system, using access rights to implement WORM functionality. The system administrator can then control what is written on the storage (though all administrator activity must be logged to ensure proof and non-repudiation).

Today, true/physical WORM is no longer suitable for all use cases (e.g., holding personal data), as it may not conform with GDPR. (Hardware WORM and software- and firmware-extension WORM implementations can circumvent this issue.)

Software WORM, however, presents its own challenges. Because it allows each software vendor to vary their implementation, this approach is the most diverse in terms of quality and reliability.

In many cases, a firmware-based WORM approach is a strong candidate. Compared to software WORM on the OS, a firmware-based approach is resistant to malware. Firmware WORM can also be used as removable media, which is not a possibility when WORM functionality is provided by the host.

There are two ways the NAND flash controller can enable WORM functionality:

In the hardware via an activated e-Fuse, which is a type of non-volatile memory with OTP (One-Time Programmable) capacity.

Through firmware extensions, where the controller’s firmware includes a write-protection flag.

One method of implementing write protection is to use a firmware-based approach. In this case, the flash controller firmware can implement a write-protection flag that is set when data is written to the memory. Once the write-protection flag is set, any attempts to modify or erase the data will be blocked by the controller. The benefits of a firmware-based approach in comparison to a software WORM on the OS is that it is resistant against malware on the host OS. Furthermore, it could be used as removeable media, which is not possible if the WORM functionality is given by the host.

As data threats continue to grow, WORM data storage is an increasingly attractive technology for industrial applications that demand robust data security and integrity. Considering the drawbacks of both true/physical WORM and software WORM, achieving optimal WORM functionality today is often with a firmware-based approach enabled by the flash controller.

Hyperstone’s flash controllers are designed with security customization and use case optimization in mind. Its API empowers engineers to develop individual, undisclosed firmware and enable WORM and other secure functionality in their drives. This allows teams to not only benefit from Hyperstone’s high-end flash management but also optimize their drive securely and independently from third parties to ensure reliable, immutable storage of critical data across applications.

The Hyperstone S9 family of flash memory controller together with provided firmware offers an easy-to-use turnkey solution for industrial, high endurance, robust flash memory cards or embedded storage solutions compatible to SD host systems up to the SD 7.1 interface standard.

Designed to satisfy industrial requirements

32-Bit core microprocessor with optimized instruction set and additional hardware accelerators for flash memory handling

hyMap® customizable sub-page-based Flash Translation Layer (FTL) enables second to random write performance, minimal write amplification and consequently the highest endurance without external DRAM

FlashXE® eXtended Endurance read-channel tuned and optimized for each Flash, advanced ECC algorithms and soft-decoding capability, read-retry, RAID and data recovery features to ensure the lowest possible read error rates

Continuously updated flash memory support

hyReliability™ flash management including superior wear leveling, read disturb management, dynamic data refresh, and power fail management ensuring the highest reliability and endurance

Advanced protection against radiation and soft-errors including, SRAM ECC and low-alpha package

Turnkey solution including firmware, manufacturing kit, test and development hardware, reference schematics, as well as health monitoring tools

Compliant to the SD Physical Layer Specifications versions 3.01 to 7.1

CPRM can be supported

Supports DS, HS, SDR12, SDR25, SDR50, SDR104 and DDR50 transfer modes

Host transfer rate of up to 104 MByte/s in SDR104 mode

Hardware support for the C2 encryption and decryption routines (CPRM)

On-chip voltage regulator for 1.8V flash memory I/O power supply

hyReliability™ flash management: superior wear leveling, read disturb management and power fail management to ensure the highest reliability and endurance

hyMap® customizable sub-page-based Flash Translation Layer (FTL) enables second to none random write performance, minimal write amplification, and consequently the highest endurance for usage profiles with emphasis on random access (e.g. JEDEC Enterprise workload)

Flexible pre-format settings for SLC caching, over-provisioning, RAID protection and performance tuning including optimization for fast boot-up times

Advanced thermal management features to maximize performance and data protection at extended temperatures

Static, dynamic, and global wear leveling

Bad block management, intelligent garbage collection and support for interleaving, cache, and multi-plane programming

Read disturb management and dynamic data refresh

Best-in-class power fail management

Firmware is stored redundantly for recovery and refresh and in-field firmware update without user data loss

High performance microprocessor core based on the Hyperstone architecture

Flexible clock frequency generation through internal oscillator and PLL

On-die temperature sensor

Automatic power-down mode during wait periods for host data or flash memory operation completion, automatic sleep mode during host inactivity periods

Supply voltage power-down detection for full power-down robustness

On-chip voltage regulator for 1.1V processor core power supply

Supports legacy asynchronous, Toggle mode and ONFI NAND

Supports ONFI SDR, NV-DDR, NV-DDR2 and NV-DDR3 transfer modes

Data transfer rate to flash memories up to 400 MByte/s

Page buffers in flexible internal memory enable optimum flash channel performance

Supports all control signals for the flash memory connection

Supports up to 4 flash memory chip selects

Supports up to 16 Kbyte flash page size

Firmware support for continuously updated for all available technologies including SLC, pSLC, MLC, pMLC, and 3D TLC as well as next generation NAND flashes

FlashXE® eXtended Endurance read channel optimized for each flash, advanced ECC algorithms with soft information decoding, read retry, RAID and data recovery features to ensure the lowest possible read error rates and maximum endurance

Flash memory power down logic and flash memory write protect control

Firmware storage in flash memory, loaded into internal memory by the boot ROM

On-chip voltage regulator for 1.2V/1.8V flash memory I/O power supply