Primary Storage vs. Secondary Storage: What's the Difference?

Statista states the global data storage market will reach over $50 billion in 2024. That’s due to the explosive growth in data organizations like yours create daily. You likely already have primary and secondary storage solutions in place, but it’s worth reviewing the purpose—and technology options—of these crucial aspects of your infrastructure.

Primary Storage: Your Frontline Repository

Primary storage, also known as main memory, is a computer component that stores data, programs, and instructions currently in use. It's located on the motherboard, allowing fast reading and writing to primary storage and providing processors with speedier access to the data and instructions it holds. Primary storage temporarily stores data that is actively in use or being processed by the system.

Primary storage is categorized into volatile and non-volatile types. Volatile storage devices lose data when power is interrupted or shut off. Standard volatile storage technologies include static random access memory (SRAM) and dynamic random access memory (DRAM). While some manufacturers feature battery backups to enable persistent storage, the data is still lost if the battery fails or is shut off.

What is SRAM?

SRAM is primarily used as a memory cache for CPUs. It is a semiconductor that consists of flip-flops—a bistable circuit composed of four to six transistors—of memory. A bistable circuit has two stable states for an input signal, so it can be used as a binary memory cell to store a logic state of 0 or 1. 

Once a flip-flop stores a bit, it keeps that value until the opposite value is stored. While SRAM gives fast access to data, its physical size is relatively large as it is used for on-chip memory. SRAM is typically faster than DRAM, with access times as short as nanoseconds. There is no need to refresh SRAM, as with DRAM, so it consumes less power and only needs a small, steady energy supply.

What Is DRAM?

DRAM is a widely used memory chip that can hold large amounts of data. Its biggest drawback is that it requires a substantial amount of power. The Enterprise Storage Forum explains that DRAM “is based on a 1T1C, or one-transistor, one-capacitor cell structure. The cells are arranged in a rectangular, grid-like array. A voltage is applied to the transistor in a DRAM cell. This voltage is then given a data value and placed on a bit-line. Once done, it charges the storage capacitor. Each bit of data is stored in a capacitor.”

The charge in the capacitor typically discharges when the transistor is turned off, so the data stored in it needs to be refreshed every 64 milliseconds. DRAM requires less physical space on a chip because it has fewer components so that it can hold more memory than SRAM. Cost is the primary benefit of DRAM.

DRAM technologies have continued to evolve with DDR, DDR2, DDR3, DDR4, and DDR5. A recent post in PC Worldnotes that DDR6 memory will gradually replace DDR5 over the next few years. Samsung forecasts that DDR6 will deliver up to 12,800 megatransfers per second (MT/s), compared to just 6,400 MT/s from DDR5.

Secondary Storage: Your Long-Term Data Repository

Per TechTarget, “secondary storage is persistent storage for noncritical data that doesn't need to be accessed as frequently as data in primary storage, or that doesn't have the same performance or availability requirements.”

While primary storage systems usually require costlier, high-performance systems, secondary storage systems typically require lower performance and greater cost efficiency. Because data in secondary storage isn’t directly accessible by the CPU, it is best used for storing data that isn’t actively used. Most often, secondary storage serves as a backup for disaster recovery purposes.

There are several technology options to consider for secondary storage. 

SSDs and HDDs

(This post explains the differences between HDDs and SSDs). While hard disk drives (HDDs) have been a standard for secondary storage for many years, Pure Storage posted on Blocks & Files last year that no more would be sold after 2028. Given that Pure’s business model is based on SSDs, that’s no surprise. However, as Forbes points out in this post, HDD sales continue to slump as SSDs displace them in many, if not most, applications and SSD prices continue to drop.

Network-Attached Storage (NAS) and Storage-Area Networks (SAN)

A NAS device lets you easily share storage across your network via Ethernet, making it ideal for collaborative environments. SANs deliver high performance using a tightly coupled network of devices dedicated to block-based data transfers between servers and storage devices. While more costly, this is essential for large-scale backup and disaster recovery efforts. 

Cloud Storage

Cloud computing and storage offer a flexible and highly scalable option for secondary storage. Even better, cloud storage offers anywhere access. Solutions like Arcserve SaaS Backup provide cloud-native data protection, backup, and disaster recovery for applications like Microsoft 365, Salesforce, and Google Workspace. 

The Role of Storage Technologies in Backup and Disaster Recovery

Primary and secondary storage systems work together to ensure data integrity and availability. Both deliver benefits for specific applications. Most organizations use a hybrid of the two.

That includes leveraging a combination of SSDs for primary storage and a combination of HDDs, NAS, SAN, and cloud storage for secondary storage. This enables you to create a balanced, efficient data storage ecosystem. Most importantly, using a backup solution like Arcserve Unified Data Protection (UDP) or SaaS Backup ensures you retain comprehensive backup critical data that can quickly be restored to your primary storage in case of a minor disruption or a massive data disaster.

When choosing your secondary storage, backup, and disaster recovery solution, look for two valuable capabilities: deduplication and compression. Read this recent post for a deep dive into how these two technologies accelerate recovery and save you money. 

Get Answers to Your Data Storage Questions

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