Compressing the operating system drive is a way to save space on a computer's hard drive. By reducing the size of files, more storage space becomes available. Since the OS drive often contains software packed with repeating assets, config files, and code, people have theorized that compressing the OS drive may free up significant amounts of space. And with transparent compression file systems available, users can seamlessly use their files without manually compressing and decompressing them.

So, should you compress your OS drive? What are the risks involved, and what does transparent compression even mean?

What Is Transparent Compression?

A file system is what structures all your files so the computer can easily store and retrieve data when necessary. Certain file systems allow transparent compression, and some do not. For example, three common file systems are used on Windows, and only one (NTFS) allows transparent compression.

Having transparent compression file systems like NFTS makes it possible to compress an OS drive. Transparent compression is a feature within a file system that automatically compresses and decompresses files, directories, and drives.

Since the file system or operating system is responsible for compressing and decompressing the files. The user can access and work with the files. Depending on the processing power of your CPU and the load it's currently in, you may or may not feel any dips in performance.

Since your OS drive contains various program files you use daily, having a transparent compression file system is crucial for machines to continually read and write files even when compressed.

What Are the Benefits of Compressing Your OS Drive?

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Compressing your OS drive became a feature in some operating systems because it provides several benefits that may be helpful for certain machines. It can be a risky process but depending on your machine and the files your OS drive contains, it may be a viable option to gain certain benefits such as:

  • Increased storage space: Compressing the OS drive leads to smaller file sizes, which allows more data to be stored in your hard drive.
  • Improved performance: With smaller files in the OS drive, computer performance may be faster, as the system can access the compressed files faster than it can access uncompressed files—but only when the CPU isn't working at full capacity.
  • Reduced backup size: Backing up a compressed OS drive results in smaller backup files, saving time and storage space.
  • Reduced network traffic: Compressed files take up less space, meaning less data must be transmitted over the network. This can be beneficial when working with remote servers or transferring large files over the internet.

Great! But there are drawbacks and even risks involved in compressing your OS drive.

Possible Drawbacks and Risks of Compressing Your OS Drive

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Having transparent file systems automatically compress and decompress files and directories are convenient ways to save space—but how about using it on the OS drive? Well, before you do, there are potentially several risks and drawbacks associated with compressing the OS drive. Here are a few of them:

  • System instability: Compressed OS drives add another layer of processing to access and write data. This can cause system instability and crashes.
  • Slow performance: In a compressed OS drive, the CPU has to use some of its resources to compress and decompress files, adding latency whenever it tries to access files.
  • Data loss: Sometimes compression may glitch out and result in data loss. Although this rarely happens, having your files constantly compressed heightens the chance you'll corrupt data.
  • Difficulty in troubleshooting: It can be difficult to troubleshoot and diagnose problems if the OS is compressed, as it can obscure the underlying issue.
  • Compatibility issues: When transferring hard drives to another computer, some systems may not support the file system or transparent compression type used in your OS drive.

The likelihood of these drawbacks will depend on your computer hardware, what files your main drive stores, and whether your OS supports drive transparent compression or not.

Which Operating Systems Support Drive Compression?

Not all operating systems natively support OS drive compression. Let's talk about those that do, those that do not, and possible workarounds.

Windows

For Windows 7 and up, Microsoft has natively enabled drive compression with their NTFS file system. Therefore, compressing your C:/ drive on Windows is the easiest as they natively support drive compression. All you have to do is to format your drive to use NTFS and then allow transparent file compression by going to your C: drive's Properties and ticking the box that says "Compress contents to save disk space."

Linux

As for PCs using Linux, they may use the Brfts file system for their OS compression. Brfts is supported by several popular Linux distros such as Arch Linux, Debian, Fedora, Ubuntu, Manjaro, and Red Hat.

Linux servers may use the ZFS file system, which is supported by Fedora, Debian, and Cent OS.

If you've been using Linux for a while, you should be able to compress your OS drive with relative ease. Although some Linux distros support NTFS, they can read and write data without the ability to change permissions.

macOS

Unfortunately for macOS, compressing your OS drive is not as straightforward as with Windows and some Linux distros. Although macOS does support transparent compression through HFS+, it doesn't provide users with the tools to do so. So, as a workaround, you'll need to install Homebrew and use third-party tools such as afsctool.

Should You Compress Your OS Drive?

In general, you are not recommended to compress your OS drive due to the potential for system instability and slower performance.

However, in some cases, it may be necessary to compress your OS drive to free up space and potentially squeeze more performance out of your PC.

If you're using an older computer, compressing your OS drive as a last-ditch effort to have a usable machine should be okay since you don't really have an option.

More modern computers may also compress their OS drives if their machine has a fast CPU and a slow hard drive. Since the CPU isn't being utilized to its full potential due to the bandwidth limitation from the hard drive, having the CPU processing the files in the background should help even out the bottleneck.

Compressing the OS Drive Should Be a Last Resort

Although compressing the OS drive is likely to save you a significant amount of storage space and may even increase performance, the risk involved is just not worth it since there are other ways you can save on storage space.

The obvious solution to your storage problem is to buy a new hard drive. But if you don't know how to change the hard drive, there are still plenty of ways to save space and increase performance. For example, you can uninstall unnecessary programs, clear temporary files, defragment your hard drive, use disk clean-up utilities like CCleaner, or just compress files and directories instead of the whole OS drive itself.

Although your operating system natively supports OS drive compression, just remember that it's really meant to be used as a last resort and shouldn't be your first option for saving disk space.