Defragment and Optimize Drives (dfrgui.exe)
Fragmentation
On a hard disk, ideally each file would be saved in contiguous clusters on the disk.
In practice, over time as files grow, they become fragmented across non-contiguous clusters, reducing read performance.
The Defragment and Optimize Drives tool (dfrgui.exe) runs various operations to speed up the performance of HDDs and SSDs:
- On an HDD:
- defragmenting rewrites file data so that it occupies contiguous clusters, reducing the amount of time the controller has to seek over the disk to read a file
- On an SSD:
- data is stored in units called blocks that are not directly managed by the OS
- drive controller determines how blocks are used according to wear-leveling routines to minimize degradation of the solid-state cells
- main purpose of the optimizer tool is to instruct the controller to run a TRIM operation
- TRIM is a process by which the controller identifies data that the OS has marked as deletable and can then tag corresponding blocks as writable
- optimizer does perform a type of defragmentation operation on an SSD if it holds the OS and the system protection feature Volume Shadow Copy service is enabled