Finding Space on a drive

aka, Where did all my space go?

Space on storage always appears to get used up way faster than we expect, and all too often we find out when it has become a problem. Most operating systems tend to slow down, have increased problems, and get downright grumpy once they run too low on space on their primary drive (such as C: for Windows or / for *nix) with 10% free space being the threshold where this starts being noticable. It is a best practice to try and keep your primary drive(s) at least 20% free. The first step is to periodically trim out temporary files and the like as described in General PC Maintenance. Of note, the scans all these tools do, take a bit of time as they do have to go through a lot of files to generate results. A typical enduser PC will take about 10 minutes to scan the whole system, where as a server volume may take an hour.

The following assumes you have rights/permissions to see all the files, otherwise you will only see those you have sufficient rights/permisssions to see at least their file system meta data.

Windows

For Windows, we have many tools to choose from, and sometimes using more than one helps find the real problems that may not be apparent in the first you use. Here are the ones I have used to good effect.

Total Commander. A general File Manager in the File Commander style that is a great alternative to Windows Exploder. To see what each of the folders have in the context you are currently, just press Alt-Shft-Enter and it will calculate it for you.

Treesize. Shows how your space is used in a 'heat map' style.

DiskFan. Fans out your drive in pie shape so you can quickly see where your space hogs are.

WinDirStat, or its many alternatives for heat maps and other visualizations.

Options+ compared

Linux

du -hx --max-depth=1 is the command to use, starting at root.
With these parameters, it will not include embedded mount points. Just start at the root of the mount point you are investigating, and cd to the folders that look too large, working you way to where the problem may be.
To view the entire file system, just remove the x, du -h --max-depth=1. From experience on none BTRFS multi drive systems, this usually just slows you down. On BTRFS systems, you just have to deal with the extra time because of how BTRFS does its Baroque "magic".

Open Enterprise Server (OES)

Remote Manager, orginally called NoRM (Novell Remote Manager), that is usually at ports 8008/8009 on each OES server since NetWare 5.1 has a wonderful analysis tool that shows you space useage by file type, age of files, and even by user.