What Is Cold Data Storage?

Cold data storage is archival storage of data that needs long-term preservation but does not require ongoing or readily available access.

Why Is Cold Data Storage Important?

Even as people and organizations generate ever-increasing amounts of data that need to be preserved long-term, the costs of this preservation continue to rise—and reliable, low-cost long-term digital storage is in short supply. The lack of cost-effective long-term storage presents challenges for large organizations that may be required by law to preserve data, and also for individuals who may want to reduce storage costs for data they want to save, such as images.

What Is Cold Data vs. Hot Data?

Cold data needs to be preserved but not readily accessed. Cold data is usually recorded on unconnected, powered-off media stored in a secure location.

Hot data needs to be accessed more frequently and is usually stored on media designed for rapid access, with multiple connections and high performance. Hot data is not suited to cold data approaches.

Is Cold Data Storage Reliable?

All forms of digital storage—including spinning hard drives, SSD (flash) storage, tape drives, and optically inscribed CDs—are susceptible to mechanical failure or environmental degradation. Compared to the longevity of countless centuries-old documents and works of art in collections around the world, digital storage is a very young technology.

Cold Data Storage Best Practices

Here are a few best practices to consider when implementing cold data storage.

Build in redundancy. Backing up never means just once, but always at least twice. Ideally, one of those copies will be stored in an entirely different physical location (for individual users, this means a process as simple as stashing a hard drive at a friend’s house). For large organizations, the solution is the same, but on a broader scale, including replacing media and hardware every few years.
Conduct periodic verification and auditing. The problem with cold storage data corruption is that the damage isn’t visible until much later. Organizations should perform periodic audits to look for irregular activity and check metadata.
Schedule assessments for data pruning. The cold data storage needs of a large organization can easily become unmanageable and expensive. Individual departments or units may be too insulated from costs to avoid defaulting to a “back up everything” mentality for the sake of convenience. The result is bloated data storage that not only raises costs but also makes it harder to gain insights from important data. To combat this issue, conduct periodic assessments that include data pruning and incentivize teams to make more efficient use of storage.

Cold Data Storage Methods

Most organizations combine the above best practices with one or more of the following storage methods:

Traditional hard drives. They’re reliable, widely available, and relatively inexpensive. However, many hard drives are not rated to last more than three to five years.
Magnetic tape drives. They’ve been used for decades for long-term data storage. Tape has proven itself to be durable over the years, and it’s also relatively inexpensive compared to other options. Properly stored tape is considered to have a lifespan of up to 30 years. However, magnetic tapes need specialized equipment for reading and writing data—equipment that may not be available decades into the future.
Cloud storage. This method has the advantages of a pay-as-you-go model, outsourced IT burdens, and universal access. However, organizations must trust that their cloud providers will follow through on maintaining, verifying, and securing data.
Hierarchical storage management (HSM). With this method, data is moved to lower storage tiers based on access frequency. Data that is rarely accessed may be archived.

Which Cold Data Storage Method Lasts the Longest?

M-DISC, a type of Blu-ray recordable disc (BD-R), claims an archival lifespan of up to 1,000 years, though this number is an estimate. Whereas regular CDs use patterns recorded in a layer of dye, M-DISCs have a layer that is actually physically engraved, making the discs more stable. M-DISCs are made by a wide variety of manufacturers. The disadvantages? Currently, 100GB is the largest capacity available, so M-DISCs are not generally suitable for large organizations. In addition, M-DISCs are dependent on the availability of Blu-ray hardware.

Capacity-optimized Storage with FlashArray//C™

The cost-per-gigabyte of flash media has dropped considerably over the years. With the release of QLC and FlashArray//C, there are a number of previously “cold” storage use cases that can benefit from the advantages flash storage brings to the table: