The difference between memory and storage or: Why has my computer gotten so slow?

One common misunderstanding about computers is just what memory is and how it affects your computer. If you're computer savvy, you probably know this already, but I wanted to answer this in a blog post because I find myself explaining this frequently, and for good reason: memory and storage are both measured in gigabytes, so they are easy to confuse.

What is memory?

Computer memory, or RAM (random access memory), is the short-term memory used by your computer to process information. When you run a program or open a document, the program or document is loaded into your computer's memory so that it can be used. The more memory your computer has, the more room your computer has to "think". Like computers, some people have more short-term memory than others (or at least more finely tuned short-term memory), allowing them to think about, evaluate, and recite more things than others.

What is storage?

Computer storage normally comes in the form of a HDD (hard disk drive, or hard drive) or SSD (solid-state drive). This is where your computer stores files and programs for long-term use. People have long-term memory, too, allowing them to recall past events without having to constantly think about them. Similarly, people can also write information down to reference at a later time.

What happens when you don't have enough memory?

When someone reads a phone number to you, some people are capable of remembering the whole number, while some people have to write down the first few digits before continuing with the remaining digits. People who can't remember all of the phone digits will need to take a lot longer to do something with that number because writing it down takes a long time. Similarly, when your computer doesn't have enough memory to do what you are asking it to do, it will have to "swap" some of that data from the memory to storage, which is often hundreds if not thousands of times slower than memory, slowing your computer drastically.

Why is my computer slower than it used to be? Do I have too many files and programs?

When you install a program or save a file to your computer, it goes into your storage. You can have as much content there as you want without slowing your computer down (with the exception of when your storage is completely full). It is only when you open documents and programs that your computer gets slower. The typical reason for a computer getting slow with age is not that your storage is too full. As programs are upgraded, the newer versions often have more features and are more complex, so we are asking our computers to do more without giving them more resources to do so. To return to the telephone number analogy, some people can remember 7 digits in their short-term memory, and some people can remember 10. Back when we only had to remember 7 digit phone numbers, people with less short-term memory did just fine. But as the area codes have become more important and we are asking people to remember 10 digits, the people who can only remember 7 digits are slowed down because they have to write the numbers down on paper. It's not that these people are less capable than they used to be or that they are becoming lazy; it's simply that, like our computers, we are asking more of them.

How much memory is enough?

Average home and office users can get by just fine with the 16 GB of memory that comes standard with most Mac models. Even if you edit the occasional video in iMovie. If you do heavy multimedia work or run virtual machines often, you should consider more. Because memory is integrated into the main processor of the computer, it cannot be upgraded in the future without replacing the computer.

How much storage is enough?

Few Mac models have upgradeable storage, so you should make sure that you get enough storage that will last you the life of your computer, which is usually 6 to 10 years. If you take a lot of videos and photos, this could be considerable. If you don't, then this might not be very much. If you are upgrading from an existing Mac, my rule of thumb is to look at your current storage and get at least double the storage you are currently using. You can find this in the Apple menu > System Settings > General > Storage.