How Does Cloud Storage Work?

It seems that cloud storage is available everywhere.

But what is it? How do you use it? Why is it valuable?

Cloud storage

Cloud storage is just keeping your files on someone else’s computer on the internet. When you install the app, it watches a special folder and automatically copies changes up and down. Put a file on one device, and it shows up on your other devices too. It feels like backup, but remember: deletes sync everywhere too.

Cloud storage is someone else’s computer

At its most basic, cloud storage is nothing more than a big computer on the internet where you can store files.

Let’s break that down a little.

• A computer. Conceptually, you can think of it as a computer with a really big hard drive, but in reality, it’s hundreds (if not thousands) of computers provided by the service provider. Put another way, you’re using your service provider’s computer(s).
• On the internet. One idea behind cloud storage is that we don’t care where that computer is, only that we can get to it from wherever we are; hence, the internet. Without an internet connection, you can’t reach your cloud storage (or even the rest of “the cloud”1).
• Where you can store files. This is what differentiates cloud storage from other cloud services: it’s just a place you can store files. It doesn’t run programs or process data in the cloud; it’s just a place to put files.

So far, so good, and there are providers that do only that: provide you with storage online and nothing else.

The providers we’re talking about today — OneDrive, Dropbox, Google Drive, iCloud, and others — build on that concept to increase their usefulness dramatically.

To understand more, we need to step back a minute and talk about copying files from one machine to another.

Floppies, USB sticks, and networks

For a long, long time, the traditional way to copy a file from one computer to another was to do so by hand. Depending on the technologies available at the time, you could:

• Copy that file to a floppy disk on one machine, take the disk to another machine, and copy the file from the floppy to the second machine.
• Copy that file to a USB stick, take that to another machine, and copy the file from the USB stick to the second machine.
• Copy the file from one machine to another across a local network.

Regardless of the mechanism you use, generally you have to do it — it’s a manual process. In fact, it’s a manual process that remains common today (except for the floppy disk part).

Enter the cloud

Cloud services become more than just a place you can put files once you install their software on your PC. The software monitors a folder specific to that service on your hard disk for any files that you add, remove, or change. When that happens, those files are added, removed, or changed in the associated online cloud storage account.

It’s called synchronization, and it’s an important concept: changes you make in one place are automatically replicated — or “synchronized” — to the other. Using OneDrive as an example:

• Add a file to the OneDrive folder on your PC, and it’s uploaded and added to your OneDrive.com cloud storage online.
• Make a change to a file in the OneDrive folder on your PC, and that change is made to the file in your OneDrive.com online. (Typically by uploading the changed file.)
• Delete a file from your OneDrive folder, and it’s deleted from OneDrive.com online.

But that’s only half the story.

Cloud storage as a copy tool

If you install the cloud service’s software on more than one machine, and you sign in to that software with the same cloud storage account, then all those devices monitor the same cloud storage and automatically synchronize the folder on their hard drives with the files stored in the cloud.

Copying a file from one machine to another now means placing that file in the cloud storage folder on your PC and waiting for it to appear in the same folder on another.

Here’s how that works:

• You place a file in, say, your OneDrive folder on computer A.
• The OneDrive software running on A notices that a new file has appeared and uploads it to your OneDrive.com account online.
• The OneDrive software running on device B notices that a new file has appeared in your OneDrive.com account online, and downloads it to its OneDrive folder.

You can do this for as many files or folders as you like until you reach the storage limitations of your online cloud service account.

Keeping things in sync

Clearly, cloud storage services can be used to copy files from point A to point B, but the concept of synchronization enables something much more complex: keeping a set of files and folders in multiple different places in sync with one another.

• You change some files on computer A, and those changes automatically show up on device B.
• You change some files on device B, and those changes show up on computer A.
• Delete files from one, and they’re deleted from the other (so you better be sure you want to delete it).
• Add files here, and they show up there as well.

Two or more machines and two or more copies of your files are always kept in sync with one another using online cloud storage as a kind of intermediary.

It’s kind of a backup — sort of but not really

Consider where we just left things: files on computer A and files on device B are automatically kept in sync with one another. You have two copies of everything, each copy on a different machine, along with a third copy stored online in your cloud storage.

Your files are in three places. It’s kind of an automatic backup that gets updated as you make changes to the files.

It is a backup because, should any one of those places disappear, the others remain. Should you lose a computer, the files are on the other computer and online. Should you lose all your devices, the online version is there, accessible via any web browser.

It’s not a backup because your online account is only “one place”, or it at least acts like one. If you delete a file2, it’s deleted everywhere at once. If you lose access to the account, the file or files may be removed from all your computers as well as online. And of course, if it’s only in one place, it’s not backed up — even if that “one place” is your cloud storage.

But by using its automatic synchronization feature, cloud storage can be part3 of a healthy backup plan.

Each online service includes additional features and functionality, of course, but this concept of storing files online and automatically synchronizing between multiple machines is perhaps the most basic and most useful feature of all.

Does “someone else” have access?

Many people have privacy concerns about keeping data in the cloud. If it’s someone else’s computer, can that “someone else” see your files?

Well, technically, they have to be able to access your files to be able to provide the cloud storage service.4 The real question is: do they?

Some people believe they absolutely do. The most common accusation is that your uploaded files are used to train the LLMs behind AI programs. Many believe that even companies without AIs aggressively use your files to build a profile, target advertising, or just about anything else that the files could be used for.

I do not believe this. I certainly don’t believe it for the major cloud storage providers like OneDrive, Dropbox, Google Drive, iCloud, and others. (Certainly other, lesser-known providers could come along and do whatever they want with the files you give them.)

However, there is one important caveat to this: these providers may be legally obligated to turn over your files in response to a court order. The only solution to keep your files private while still using their services is to proactively encrypt your files before they’re uploaded. Tools like Cryptomator are built for exactly this.

But, naturally, whether you’re willing to use these services at all will depend in part on your level of trust that your data will remain private.

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