Low Disk Space – The #1 Performance Killer

No matter how fast your PC is, there’s one thing slowing it down and that is low disk space. It’s probably the no. 1 cause of a sluggish machine and even one that IT pros tend to overlook. In this blog post, I’ll explain why low disk space can make every program slow down to an absolute crawl, increase load times, and cause dozens of error messages. I’ll also explain how to quickly regain gigabytes of data and improve your PC’s performance.

Why low disk space affects PC performance

Windows and most third-party programs need disk space to “breathe”. For example, Windows creates a paging file on your hard disk to extend your PC’s physical memory (RAM). This is done just in case the space runs out. Even on systems with 2 GBs or 4 GBs, this paging file is frequently used. Low disk space means that the paging file can’t grow when required, thus heavily reducing PC performance.

Depending on its demand, the paging file dynamically increases and decreases in size. Imagine if your disk space falls below the 500–1000 MB limit. Once the paging file tries to increase and hits the disk space limit, you can expect terrible performance, and your system will most likely crash.

And Windows isn’t the only system that depends on at least a couple of GBs of free disk space. Many applications create files to store data temporarily. Photoshop, for example, is known to create a “scratch disk” when running. This disk has a dynamic size ranging from a couple of hundred MBs to several GBs. This can cause a lot of outcry as seen here, and this user suffered when Photoshop created a temporary file with a size of 43 GB. Expect Photoshop or any other application for that matter to run terribly or not at all once this temporary file takes up the rest of your hard disk limit.

Unfortunately, this problem persists on modern machines. Take a netbook, a low-budget notebook, or even a high-end machine. Your music library or even your entire set of stored photos might just be enough to hit the limit quickly, add to that the regular size of a typical Windows installation (20 GB) and your applications, and you’re working at the limit of your disk’s capacity.

SSDs (Solid State Drives) are even more prone to slowdowns if there is no (or next to no) disk space available. This is because SSDs choose empty blocks for write operations, as they’re only capable of deleting and rewriting a block. If you’re running low on disk space, most or all of these blocks are partially filled. The result: The SSD has to erase and rewrite the blocks. It literally needs to read the data block into cache, delete the block, modify the data in cache, and then rewrite the block. It’s just an additional operation that is not necessary and can slow things down immensely.

Massive performance hits confirmed

Am I just blowing smoke, or is this a serious performance threat? It really is, in fact! I’ve tested this theory several times. I really didn’t have to work hard on my main machine (an Intel Penryn C2D with 3 GHz, 4 GB of RAM, and an SSD). My primary boot partition is exactly 100 GB in size, and I use the other 100 GBs for operating system testing purposes. My “Programs” folder takes up 6 GB, while the Windows folder takes up 21 GB. However, the big storage eater is my iTunes folder, as I have about 10 GB of music, 3 GB of apps, and 30 GB of TV shows. In total, I’m looking at 42.8 GBwhich means I only have a couple of GB left! What I did in order to run low on disk space is easy: I simply duplicated a couple of files (several hundred MB) until I hit the disk space limit.

To my surprise, once my disk space sank below the dangerous 100 MB mark, the PC didn’t suffer. This is probably due to the fact that both my RAM and the default paging file compensated for the current memory need. However, things got shaky once I started to work more heavily and hit the limit. All of a sudden, programs and applications (aside from very low-resource tools like SnagIt 10 and TuneUp Utilities 2011) wouldn’t start and those I was currently running didn’t respond. iTunes, for example, didn’t react to any clicks. It froze but kept playing music in the background. Oddly enough, plugging a USB hub in didn’t work at all.

This is unheard of but probably because device memory allocation didn’t work properly. Once I recovered the free space, everything was fine again.

Unfortunately, the PC’s performance took a turn for the worse when it was low on disk space. The boot procedure took more than twice as long, according to XPerf from Microsoft’s Performance Toolkit.

Since many of my regular programs refused to launch once I hit the total memory limit (the physical RAM plus the paging file), I couldn’t benchmark a whole lot of application start-up times. After trying Outlook, Photoshop, InDesign and even Live Messenger, I found that only Internet Explorer 9 launched with only a couple of MBs of free disk space left. Here are the drastically bad results:

Yes, time literally stood still the moment I clicked on the web browser icon as nothing happened. I couldn’t launch another program or Windows Explorer—not one thing! After about 13 seconds, the web browser appeared on the screen and started to load a website. Just horrible, and that’s basically all I could do under this heavy load. The system was absolutely unusable.

We can all agree that low disk space is a performance killer given these results. So, what can we do to improve PC performance?

Rescue your system—NOW!

If you’re running out of disk space, you should definitely check out our “Five Ways to Get Rid of Data Clutter” blog post. You’ll learn how to:

• Use TuneUp Utilities 2011′s “Gain Disk Space” feature to remove unnecessary files and old backups
• Use TuneUp Disk Space Explorer to find huge data hogs
• Use Microsoft’s Windows Disk Cleanup tool
• Clean third-party apps
• Uninstall Windows features you might not need
• Get rid of huge programs that you don’t need anymore

Most importantly, keep a close eye on your free disk space!