RAM Is Cheap: Why Not Run Everything From Memory?

The Affordability of RAM and Operating System Execution

The cost of RAM modules has significantly decreased recently. This raises a pertinent question: why isn't the entire operating system being loaded and run directly from exceptionally fast RAM?

Origin of the Question

This particular question and its subsequent answer were originally posed and discussed on SuperUser.

SuperUser functions as a specialized segment within Stack Exchange, a network of collaboratively edited question and answer websites.

Stack Exchange is built upon a community-driven model, where users contribute to and refine the knowledge base.

Exploring the Potential of RAM-Based Operating Systems

Despite the increasing affordability and speed of RAM, several factors prevent a widespread shift to running operating systems entirely from it.

• Volatility: RAM is volatile memory, meaning it requires constant power to retain data.
• Persistence: Operating systems and user data need to be persistently stored, which RAM cannot provide without continuous power.
• Cost/Capacity Trade-off: While RAM is cheaper than it once was, a capacity sufficient to hold an entire operating system and user applications would still be expensive.

Alternative Approaches

Instead of a full RAM-based OS, techniques like RAM disks are used for specific purposes.

A RAM disk utilizes a portion of system RAM to simulate a physical disk drive. This can significantly speed up access to frequently used files.

However, data stored on a RAM disk is lost when the system is powered off, limiting its use to temporary files and caching.

Addressing the Inquiry About RAM-Based Systems

A SuperUser user, pkr298, has posed a compelling question regarding the feasibility of utilizing RAM instead of traditional disk-based storage for computer operations. His core idea centers around the speed and decreasing cost of RAM.

The User's Proposition

pkr298 suggests that given the speed advantage of RAM over SSDs and the declining price of memory, it would be logical to load the entire operating system and applications into RAM upon startup.

He further postulates that, assuming data persistence isn't a primary concern, running a computer entirely from RAM could significantly enhance performance.

“RAM is cheap, and much faster than SSDs. It's just volatile. So why don't computers have a LOT of RAM, and on power up, load everything to the RAM from the hard drive/SSD and just run everything from there, assuming there's no real need to persist anything outside of memory? Wouldn't computers be much faster?”

“Of course, current operating system may not support this at all, but is there any reason RAM isn't used this way?”

Why RAM-Based Systems Aren't Prevalent

While the concept appears straightforward, several factors prevent the widespread adoption of entirely RAM-based computing systems.

The primary obstacle is the volatility of RAM. Data stored in RAM is lost when power is removed, necessitating a constant power supply or a rapid save-to-disk mechanism.

Challenges and Considerations

• Data Persistence: Maintaining data integrity during power outages requires robust backup solutions.
• Capacity Costs: While RAM prices have fallen, equipping a system with enough RAM to hold an entire operating system, applications, and user data remains expensive.
• Operating System Support: Traditional operating systems are designed to work with persistent storage and would require significant modifications.
• Boot Process: The initial loading of the operating system into RAM from a slower storage device would create a bottleneck.

Although current operating systems may not inherently support this approach, the fundamental reason RAM isn't universally employed in this manner lies in a combination of practical limitations and cost-benefit considerations.

The inquiry highlights a valid point about performance gains, but the challenges associated with volatility, capacity, and system architecture currently outweigh the benefits for most users.

Why Disk-Based Systems Remain Prevalent

A SuperUser community member, Hennes, provides valuable insights into the reasons why disk-based storage continues to be utilized despite the availability of RAM.

Reasons for Not Utilizing RAM as Primary Storage

Several factors contribute to the continued reliance on traditional disk systems. While RAM is becoming more affordable, it isn't inexpensive enough for large-scale implementation, particularly when considering the capacity needed for modern applications.

• Cost: Although DDR3 RAM is relatively cheap, the expense increases significantly when purchasing large DIMMs.
• Volatility: RAM is volatile, meaning it loses data when power is removed. This necessitates reloading all content upon system startup, which can introduce substantial delays. For example, a 100GB RAM disk would require approximately two minutes to copy data from the disk during boot.
• Power Consumption: RAM consumes more power than SSDs, typically around 2-3 Watts per DIMM.
• Motherboard Limitations: Motherboards generally have a limited number of DIMM slots, usually six or fewer. Increasing the number of slots adds to the board's size and cost.
• System RAM Requirements: Sufficient RAM is also needed to run programs concurrently with any potential RAM disk implementation.

Despite these challenges, RAM disks do exist. They are available as PCI boards with DIMM sockets and as specialized appliances designed for very high Input/Output Operations Per Second (IOps).

However, these solutions are generally quite expensive.

Examples of RAM Disk Cards

There have been several low-end RAM disk cards that have reached production status.

It's important to note that creating a RAM disk within standard system memory is not the only approach.

Alternative Approaches to Volatile Storage

Several alternative methods can be employed to achieve volatile storage:

1. Utilizing a dedicated physical drive with volatile (dynamic) memory, accessible via SAS, SATA, or PCI Express interfaces.
2. Employing battery-backed storage, which retains data even during power outages without requiring initial data copying.
3. Using static RAMs instead of DRAMs, although this is typically a more expensive option.
4. Leveraging flash or other permanent storage for data retention, but this introduces limitations related to write cycles. Using flash solely for storage effectively results in an SSD.

The discussion extends to more complex topics like Amiga RAD: reset surviving RAM disks, IOPS, wear leveling, and other advanced considerations. However, a comprehensive exploration of these areas is beyond the scope of this overview.

Cost Comparison

A comparison of DDR3 and SSD pricing illustrates the cost difference:

• DDR3: Approximately €10 per GiB, or €10,000 per TiB.
• SSDs: Significantly less expensive, ranging from 1/4th to 1/10th the cost of DDR3.

For further information on RAM disks, refer to the article RAM Disks Explained: What They Are and Why You Probably Shouldn't Use One. (Replace with actual link)

Readers are encouraged to share their thoughts and contribute to the discussion in the comments section. Additional insights from other tech-savvy users can be found in the full discussion thread. (Replace with actual link)