Enterprises are generating huge volumes of data every year, with an average annual data growth of 40-50 percent. This growth has to be handled using IT budgets that are only growing at an annual average of 7 percent. Such disproportion creates a challenge for mainframe professionals. How can they store all this data cost-effectively?

Particularly challenging is deciding on the right strategy for long-term storage, also known as cold storage, for archived data that is rarely or never accessed. There can be different causes for keeping such data for the long term, which often lasts years or even decades:

• Financial data is stored for compliance and might be required in case of an audit.
• Legal information must be kept in case of legal action.
• Medical archives are stored in vast quantities and their availability is highly regulated.
• Government data has to be stored for legal reasons, sometimes even indefinitely.
• Raw data is stored by many enterprises for future data mining and analysis.

Desired attributes of a cold storage solution

Cold storage, also referred to as “Tier 3 storage,” has different needs than Tier 0 (high-performance), Tier 1 (primary), and Tier 2 (secondary) storage. These are some of the considerations to keep in mind when designing your cold storage solution:

• Scalability – As the amount of generated data on average doubles in less than two years, your cold storage technology accordingly needs to be infinitely scalable.
• Cost – Cold storage must be as inexpensive as possible, especially because you will need a lot of it. Luckily, as it is rarely accessed it allows compromising on accessibility and performance, which can be leveraged to reduce cost.
• Durability and reliability – Reliability is the ability of a storage medium not to fail within its durability time frame. Both are important to check, and you will find that some cold storage options are durable but not necessarily as reliable as others, and vice versa.
• Accessibility – Cold storage is meant only for data that does not need to be accessed very often or very rapidly, yet the ability to access it is still important. As mentioned above, compromising on this aspect enables a lower cost.
• Security – The security of cold data is vital. If it is stored onsite you need to take the same security precautions as with your active data. If it is in the cloud, you must ensure the vendor has proper security mechanisms in place.

Cold storage technology options for mainframe

Mainframe professionals have three general technology options when it comes to cold storage: tape, virtual tape, and cloud. While tapes are still the dominant cold storage media for mainframes, cloud is gaining momentum with its virtually limitless storage and pay-as-you-go model.

Here is a summary of these technologies, and their relative advantages and disadvantages: