How to allow ArcGIS to build a large transportation network dataset

Sometimes when building a large network dataset (in my case 100M ~ edges) in ArcGIS, "Build network dataset" tool returns "read/write error". I at first thought it was because the feature class source was somehow corrupt, but it turned out to be insufficient temporary directory space.

Problem: ArcMap or ArcCatalog returns “read/write error” while building a transportation network dataset.
Cause: insufficient temporary directory space
Solution: Secure enough free space in TEMP directory.

A new window opens and displays the contents of the System Temporary Directory. When building a very large network dataset (for example, all of the streets in France), hundreds of gigabytes of temporary space may be required to process a task of this size. If there is not enough disk space in the current TEMP directory to perform the task, it is necessary to change the TEMP directory to a location that has sufficient memory. The following steps show how to make this change.

1. Right-click Computer and click Properties.
2. Click Advanced system settings on the left panel to display the System Properties dialog box, and click the Advanced tab.
3. Click the Environment Variables button.
4. In the Environment Variables dialog box, under User variables for , both TMP and TEMP may listed. This is the common location; each different login account is assigned its own temporary location.
5. Click the Edit button. In the Edit User Variable dialog box, under Variable value, specify the path to the directory that Windows and many other programs uses for temporary files. Change this to a location that has sufficient disk space to process the network dataset. 
6. Repeat this process for both the TMP and TEMP directories.
7. Restart Windows to begin using the new value for temporary files. Restart any running programs for the new value to take effect.

http://support.esri.com/de/knowledgebase/techarticles/detail/40743

Another lesson to keep free space in the boot drive.