Actual vs. Allocated Disk Space

Some software tools, including our FolderSizes disk space analyzer, are capable of reporting two size metrics for each file system object it encounters – “size” and “allocated size” (the latter is sometimes also called “size on disk”). In this blog entry, I will discuss what these metrics represent and how they differ.

Disk space is allocated to files in units called clusters. The size of a cluster can vary depending upon several factors, including what file system is used (NTFSFAT32, etc.) and partition size. Most people today running the Microsoft Windows operating system are using NTFS, which has a default cluster size of 4K (4096 bytes).

Since all files are stored within one or more clusters, their “size on disk” (allocated size) is always a multiple of the file system’s cluster size. For example, if you are using NTFS with a 4K cluster size, any file containing between 1 and 4096 bytes of data will consume a single cluster. Any file containing between 4097 and 8192 bytes will use two clusters. And so on.

As a result, any file that has a size which is not an exact multiple of the file system’s cluster size (and the vast majority aren’t) will “waste” a portion of its last cluster. Therefore, a file’s “allocated” size will usually be larger than its actual size. This wasted space is generally referred to as “cluster overhang” or “disk slack.” Some tools (including FolderSizes) can also report upon cluster overhang for folders (directories).

A rough estimate of wasted space for a volume can be calculated by multiplying the number of files it contains by half the cluster size. So, for example, if an NTFS file system with 4K clusters contains 50,000 files, the estimated wasted space would be about 97MB of disk space.

Other factors, such as file system compression can also affect the computation of allocated space.

Posted: July 7, 2020 2:03 am

FolderSizes 9.1 Released

FolderSizes v9.1 has been released and is now available for download. There are a few notable changes in this build that we’d like to review.

First, we’ve made dozens of user interface enhancements that include the re-introduction of a dark theme (by popular request) and improvements to existing themes. We’ve also improved the scaling of UI elements for high-resolution monitors – including revised icons, enhancements to the installer, better print scaling, and much more.

There are many changes “under the hood” as well, including improved behavior when analyzing DFS shares, improved PDF exports, and various bug fixes.

And finally, the minimum Windows OS requirements have been updated to Windows 7 SP1 or later (or Windows Server 2012 R2 or later). Anyone needing support for older operating systems (Windows Vista, Server 2008) can still download and install the previous FolderSizes v9.0 release.

P.S. We also recently released Permissions Reporter v3 – a major version upgrade to our world-class NTFS permissions reporting solution. We hope you’ll give it a try.

Posted: June 19, 2020 10:06 pm

Silent Installation & Licensing

FolderSizes v9 enhances the product installer to allow customers to apply a license key during (optionally silent) installation.

To use this feature, invoke the FolderSizes v9 installer with the following syntax:

“fs9-setup.exe” LICENSE_CODE=”XXX-XXX-XXX-XXX”

In practice, it will usually be necessary to fully qualify the path to the installer executable. For example:

“c:\myfolder\fs9-setup.exe” LICENSE_CODE=”XXX-XXX-XXX-XXX”

Note that you can combine this capability with one of the following silent installation flags:

– basic UI: /qb (only a progress bar will be shown during the installation)
– no UI: /qn (no UI will be showed during the installation)

And now a final example that installs FolderSizes 9 silently and applies a license key:

“c:\myfolder\fs9-setup.exe” LICENSE_CODE=”XXX-XXX-XXX-XXX” /qn

Posted: June 13, 2019 7:29 pm

FolderSizes 9 Now Available

Key Metric Software has released FolderSizes 9 – a new major version of our world-class disk space analysis software for Windows.

With over a year of development and testing under its belt, FolderSizes 9 introduces sweeping improvements to nearly every feature and function offered by the product. Over a hundred enhancements and fixes make this version of FolderSizes our best yet.

For a high-level overview of what’s new in FolderSizes 9, please see:

Or head straight for the download page and try it for yourself:

In addition to all the feature enhancements, we’ve also added support for consultant licenses. These allow consulting individuals and companies to use FolderSizes 9 to service their customers broadly, and at reasonable prices.

FolderSizes 9 also finally ends our long-standing support for Windows XP and Server 2003. Microsoft stopped supporting these operating systems back in April of 2014, so it was (probably well past) time for us to do the same. FolderSizes 9 also looks forward by adding official support for Windows Server 2019 and the latest builds of Windows 10.

I’m amazed, at times, when I look back at the growth of FolderSizes since its introduction in 2003. That’s over 16 years of continuous development. And we have no intention of slowing down. So check out the new version and let us know what you think… because we’re always planning for the future.

Posted: May 16, 2019 4:14 am

FolderSizes 8.5 is Released

Key Metric Software is proud to announce the release of FolderSizes 8.5.

The main goal of this release is enhanced support for high resolution displays. We’ve tweaked every aspect of the user interface to ensure correctness in high DPI environments, and now FolderSizes looks and performs beautifully on 4k monitors with display scaling all the way up to 200% (and everything in between).

A range of additional minor feature enhancements and bug fixes are also included in the FolderSizes 8.5 release. And if you’re a FolderSizes v8 license owner, this update is entirely free.

Download the latest version of FolderSizes today.

Posted: March 5, 2018 9:06 pm