Looks like Windows 8 introduces some additional DEFRAG options.
| Option | Description | Option Available | |
| Windows 7 | Windows 8 | ||
| /A | Perform analysis on the specified volumes | Yes | Yes |
| /C | Perform the operation on all volumes | Yes | Yes |
| /D | Perform traditional defrag (this is the default) | No | Yes |
| /E | Perform the operation on all volumes except those specified | Yes | Yes |
| /H | Run the operation at normal priority (default is low) | Yes | Yes |
| /K | Perform slab consolidation on the specified volumes | No | Yes |
| /L | Perform retrim on the specified volumes | No | Yes |
| /M | Run the operation on each volume in parallel in the background | Yes | Yes |
| /O | Perform the proper optimization for each media type | No | Yes |
| /T | Track an operation already in progress on the specified volume | Yes | Yes |
| /U | Print the progress of the operation on the screen | Yes | Yes |
| /V | Print verbose output containing the fragmentation statistics | Yes | Yes |
| /X | Perform free space consolidation on the specified volumes | Yes | Yes |
There is little information yet about these options but I assume that they might have to do with the rumored new “protogon” file system and that there is more support for SSD included.