One case I came across early last year:
One server recently raised red alert – 85% of C drive had been occupied and that raised red flag on this server.
Here is some basics I found on the server:
C drive of this server is 60G, entire file system on C drive takes 17G and free space is 12G.
Where did that missing space go?
It turned out be there is 32GB page file (swap file in some other systems)!
This page file in Windows, is defaulted to 1.5 times physical RAM (32G on this server), therefore, it might go up to 48G:
After finding the trouble maker, everything else seems easy:
This wasn’t an issue on 32Bit system because RAM was limited at 4G (1.5 times is 6G, relatively small compare to a 60G hard drive). In 64 Bit system, RAM is unleashed and it does become an big consumer of C drive.
Options we had includes:
1. Expand C drive or relocate page file to another drive. This is probably the easiest way to do with extra expense.
2. Monitor system paging with real activities and determine an acceptable limit for page file size. For more details, see Microsoft website: http://support.microsoft.com/kb/2021748
Last point I wanted to make it is, since servers can own significantly more RAM, page file size should be part of consideration for provisioning: make sure you have enough space to cover page file!