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Why does CrashPlan report a different number of files than my computer?

Applies to:
  • CrashPlan PRO
  • CrashPlan PROe

Overview

If you compare the number of files on your computer to the number of files CrashPlan says it's backing up, you may notice a difference. This article explains why there can be a discrepancy between your computer and CrashPlan, and why there's no reason to worry about it.

Compare the number of files reported by CrashPlan to your computer

You can see information about a folder, including the number of files it contains and its total size, with the Properties (Windows) or Get Info (Mac) command. You can access these commands by right-clicking (Windows) or control-clicking (Mac) on a folder.

If you compare the number of files reported by your computer to the number of files reported by the CrashPlan app for the same folder, you may notice a difference: CrashPlan often says it's backing up more files than Windows Explorer or the Finder says the folder contains.

For example, imagine you're on a Mac and use the Get Info command on a folder of pictures. The Finder might report that the folder contains 4,567 items, while CrashPlan reports that it's backing up 4,676 files in that same folder.

Don't worry - CrashPlan is working as designed. Read on to find out why this discrepancy occurs.

CrashPlan reports more files than my computer

Every computer contains hidden files that don't display by default when you're browsing files (examples include ”.DS_Store” and ”desktop.ini” files). They're hidden because they aren't files you use directly, but your computer uses them to operate.

CrashPlan detects hidden files and backs them up, just like it backs up the files that you can see. The combined total of normal files and hidden files is the total reported on the Backup tab of the CrashPlan app. As a result, CrashPlan may report that it is backing up more files than your computer.

CrashPlan reports smaller total file size than my computer

It's also possible that the CrashPlan app reports backing up less total data than your computer says it's storing. For example, your operating system may report that a folder takes up 10 GB of space, but the CrashPlan app says it's only backing up 9 GB from that same folder. There are several reasons that this may happen:

Calculation differences

Even after accounting for excluded files, you might see a file size discrepancy between what the total reported on the Backup tab and the total reported by your computer for the same folders.

Calculation background

When human beings think about storage space, we calculate in a base-10 counting system. That is, a kilobyte is 1000 bytes, a megabyte is 1000 kilobytes, and a gigabyte is 1000 megabytes.

When your computer calculates storage space, it calculates in a base-2 counting system, or binary. For a computer, the storage unit of 1 gigabyte is equal to exactly 1024 megabytes, because it arrives there by multiplying 2 times 2 times 2...until it approximates 1000.

The practical result of this is that you and the computer can both measure the same thing, but the label used is different. Think of it like the difference between miles and kilometers. You can say that one mile equals 1.6 kilometers (or that one kilometer equals 1.62 miles). But no matter what measurement system you use, they both refer to the same amount of space.

Calculation results

To keep CrashPlan's functions streamlined and efficient, it "speaks" to your computer using the computer's native language of base-2. But on the Backup tab, it uses base-10 to report the total to you.

So if your computer says a folder is 1 MB in size, CrashPlan reports it as about 96% of that amount--the difference between 1024 and 1000. If it's 1 GB, the amount reported is closer to 93%, and so on as the volume increases.

The bottom line

CrashPlan is working as expected, and you shouldn't worry that your files aren't being backed up. If you'd like to learn more about these topics, check out the External Resources below.

External resources

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