I often hear people saying that they need to get more memory for their computers. Sometimes I’ll ask how much they have now, and I’ll usually get an answer like, “Oh, 250 gigs.”
No, you don’t have 250 gigs of memory. You have a 250 gig hard drive, also known as “storage.” Chances are you have 1, 2, 4, or possibly even 8 gigs of memory. Let me explain.
“Memory” (“Random Access Memory,” or “RAM”) is like your brain; it’s fast, immediately available, but limited in capacity. It’s also relatively expensive (computer memory, that is; your brain is priceless). DDR memory runs around $27 per gigabyte (depending on speed, and density; more gigs per “stick” usually means a higher price per gig). Locating an item of data in memory is close to instantaneous. We’re talking about nanoseconds here. The data in RAM goes away – is “forgotten” – when the power is shut off.
“Storage” is like a filing cabinet. It has lots of capacity (a 250 gig “filing cabinet” or hard drive) and you can expand it pretty easily either by buying a larger filing cabinet, or adding another one. However, it’s fairly slow, compared to memory. But it’s inexpensive; a terabyte (1000 gig) hard drive retails for around $60 to $70 now. That’s about 7 cents a gigabyte.
The speed difference is why you want as much memory as your operating system and budget can handle; the more information you can keep in memory (as opposed to storage), the faster your computer will operate. When your memory is full, the operating system swaps some of it out to the hard drive, into a file known as “virtual memory,” but due to the speed issues with hard drives, you want to avoid that as much as you can. A very fast hard drive will still require 6.4 milliseconds (ms) to access some random data; that’s nearly a thousand times slower than memory.
And now that sold-state drives (SSDs) are getting somewhat affordable (64 gigs for $128, or about $2 per gigabyte), does that mean there’s no difference between memory and storage? Absolutely not! A very fast (And very expensive) SSD still needs 0.10 ms for random access. That’s still a hundred times slower than RAM.
So that’s why your computer never “runs out of memory;” it swaps memory out to storage as needed. The more RAM you have, the less often it has to be swapped out. When you “hibernate” your computer, everything in RAM is written out to a file on the hard drive, and then the computer is shut off. When you wake the computer from hibernation, that information is reloaded into memory, and you can pick up right where you left off. The trade-off here is that the more memory you have, the longer it takes to save or load it for hibernation.
So, is that clear? While you may indeed need more memory for your computer, it’s pretty unlikely that you have 250 gigs already, unless you spend over $6000 on memory. And every time you confuse memory with storage, a geek someplace dies a little inside.